PROSTAGLANDINS
PROSTAGLANDINS
J.R.G.
Challis,
S.R.
IN THE C I R C U L A T I O N
Dilley,
J.S.
OF THE FETAL LAMB
Robinson,
G.D.
Thorburn
U n i v e r s i t y of Oxford, N u f f i e l d Institute for M e d i c a l Research, John Radcliffe Hospital, D e p a r t m e n t of O b s t e t r i c s & Gynaecology, H e a d l e y Way, Headington, Oxford.
ABSTRACT P r o s t a g l a n d i n E and PGF have b e e n m e a s u r e d in the p l a s m a of c h r o n i c a l l y c a t h e t e r i z e d fetal lambs throughout the last 20-35 days (0.73 onwards) of gestation. The m e a n c o n c e n t r a t i o n of PGE was higher than that of PGF. There was a s i g n i f i c a n t increase in the c o n c e n t r a t i o n of PGE but little change in the c o n c e n t r a t i o n of PGF in samples of fetal plasma taken w i t h i n 24 h of parturition. In contrast, at this time in m a t e r n a l u t e r o - o v a r i a n venous plasma, there was a large increase in PGF, but r e l a t i v e l y little change in PGE. There was a s i g n i f i c a n t d e c r e a s e in the c o n c e n t r a t i o n of PGE and PGF in the plasma of lambs w i t h i n 12 h after b i r t h compared to the levels found in the same animals as fetuses a few hours previously. The p h y s i o l o g i c a l importance of these changes is discussed.
ACKNOWLEDGEMENTS We thank Mr. A. Stevens, Ms. C. Forster, G. Pooley, P. H a r t l e y and Mrs. L. C l o v e r for their e x c e l l e n t technical assistance, and Drs. J. Hennam, B.J.A. Furr, and May & Baker Ltd. for g e n e r o u s l y supplying antibodies. The w o r k was s u p p o r t e d by an M.R.C. Grant.
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INTRODUCTION Recent studies h a v e s u g g e s t e d that p r o s t a g l a n d i n s may be i n v o l v e d in v a r i o u s aspects of fetal p h y s i o l o g y . The i n f u s i o n of PGE 2 into fetal lambs r e s u l t e d in c a r d i o v a s cular changes in the fetal c i r c u l a t i o n and p l a c e n t a l b e d (i). In addition, d i f f e r e n t p r o s t a g l a n d i n s may e i t h e r c o n s t r i c t or dilate the ductus a r t e r i o s u s of fetal lambs and fetal calves in vitro (2, 3), and the a d m i n i s t r a t i o n of i n d o m e t h a c i n to ewes (4) or rats (5) during late pregnancy provoked p r e m a t u r e c losure ~ the ductus a r t e r i o s u s in utero i m p l y i n g that p r o s t a g l a n d i n s were i n v o l v e d in m a i n t a i n i n g the p a t e n c y of this vessel. D e s p i t e the a p p a r e n t i m p o r t a n c e of p r o s t a g l a n d i n s in the fetus, e s t i m a t e s of p r i m a r y p r o s t a g l a n d i n s have b e e n r e s t r i c t e d largely to m e a s u r e m e n t s of their c o n c e n t r a t i o n s in a m n i o t i c f l u i d or u m b i l i c a l cord p l a s m a (see 6). These e s t i m a t e s h a v e o r t e n b e e n on single rather than serial samples. However, the d e v e l o p m e n t of procedures for imp l a n t i n g and m a i n t a i n i n g v a s c u l a r c a t h e t e r s in fetal lambs t h r o u g h o u t laie p r e g n a n c y p e r m i t s b l o o d samples to be taken s e r i a l l y f r o m the c o n s c i o u s fetus in utero. U s i n g this p r e p a r a t i o n , the p r e s e n t study was d - ë s ~ n e d to measure the c o n c e n t r a t i o n s of PGE a n d P G F in serial samples of fetal plasma. We w i s h e d to e s t a b l i s h w h e t h e r the p r o s t a g l a n d i n levels c h a n g e d during p r e g n a n c y , p a r t i c u l a r l y in r e l a t i o n to p a r t u r i t i o n , w h e n the c o n c e n t r a t i o n o f PGF in the u t e r o - o v a r i a n vein is k n o w n to rise (see 7), and after birth, as p u l m o n a r y b l o o d flow i n c r e a s e s in the n e w b o r n (8). MATERIALS
AND M E T H O D S
Animals The live sheep u s e d in these e x p e r i m e n t s were Border L e i c e s t e r x S u f f o l k cross. The day of marking by an intact ram was taken as day zero of p r e g n a n c y . Fetal c a t h e t e r s were i m p l a n t e d u n d e r c o n d i t i o n s of strict asepsis b e t w e e n days 106-126 of p r e g n a n c y . The ewes w e r e a n a e s t h e t i z e d w i t h t h i o p e n t o n e (i g i.v.), and maint a i n e d w i t h f l u o t h a n e a n d oxygen. The uterus was e x p o s e d by a m i d - l i n e s u b - u m i l i c a l incision, and in four of the animals the fetal h i n d limb was l o c a t e d and e x p o s e d b y a small i n c i s i o n through the ußerine wall. Loss of a m n i o t i c f l u i d was p r e v e n t e d u s i n g Allis forceps to clip the skin to the u t e r i n e wall. A c a t h e t e r (PP 90 i.d. 0.86 mm., o.d. i.i mm., Portex) was i n s e r t e d into a f e m o r a l artery, such that its tip lay in the dorsal aorta. The c a t h e t e r was
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s u Z u r e d Zo The skin» Zhe fetal limb replaced» and Zhe a m n i o t i c sac and u Z e r u s c l o s e d in a single layer. In the f i f Z h animal Zhe feZal h e a d was l o c a Z e d a n d e x p o s e d , a n d a c a Z h e Z e r (PP 90, PorZex) was i n s e r Z e d inZo a fe±al jugular rein. The feZal c a Z h e Z e r s w e r e e x Z e r i o r i z e d Zhrough a small f l a n k incision, a n d f i l l e d w i Z h sZerile h e p a r i n saline (500 uniZs/ml). In Zhree of Zhe animals a sofZ vinyl c a Z h e Z e r (i.d. 1.0 mm., o.d. 1.5 mm.» Dural PlasZics) was imp l a n Z e d inZo a main u Z e r o - o v a r i a n vein Z h r o u g h a small ZribuZary» and e x Z e r i o r i z e d Zhrough Zhe flank of Zhe ewe. Vinyl c a Z h e Z e r s (sofZ vinyl 4, PorZex, i.d. 2 mm.) were i n s e r Z e d inZo a m a Z e r n a l c a r o Z i d arZery and exZernal j u g u l a r vein. All Zhese c a Z h e Z e r s w e r e f l u s h e d and f i l l e d w i Z h h e p a r i n - saline (500 uniZs/ml). B l o o d samples (i0 ml. f r o m the maternal vessels; 6 ml. f r o m the fetal vessels) were drawn e v e r y other day inZo h e p a r i n i z e d syringes, and Z r a n s f e r r e d i m m e d i a Z e l y Zo c h i l l e d Zube~. The b l o o d was c e n Z r i f u g e d i m m e d i a Z e l y aZ 2000 x g aZ 4 C for 15 min A a n d Zhe p l a s m a was d i v i d e d inZo aliquoZs a n d s Z o r e d aZ - 2 0 - C unZil assayed. B l o o d samples (i ml) for b l o o d gas and p H a n a l y s e s w e r e c o l l e c Z e d ~ sZerile h e p a r i n i z e d glass syringes. In order to e s t a b l i s h b a s e line v a l u e s for the conc e n t r a t i o n of p r i m a r y ~rostaglandins in the ~ a s m a of adult sheep» samples w e r e ±aken by v e n e p u n c t u r e f r o m the jugular r e i n of 12 n o n - p r e g n a n t ewes at r a n d o m stages of the o e s t r o u s cycle. The b l o o d was c o l l e c t e d into h e p a r i n i z e d syringes, t r a n s f e r r e d to c h i l l e d tubes, and immediately c e n t r i f u g e d at 2000 x g for 15 min. The p l a s m a was d i v i d e d into aliquoßs, a n d s t o r e d at - 2 0 ° C until assayed. B l o o d Gas M e a s u r e m e n ± s . The P02, p C O 2 and p H of the maternal a n d fetal b l o o d samples were m e a s ü r e d u s i n g a R a d i o m e t e r Model 27. Haematocrits w e r e m e a s u r e d u s i n g a micro c e n t r i f u g a t i o n procedure. Radioimmunoassay. C o r t i s o l was m e a s u r e d by a r a d i o i m m u n o a s s a y p r o c e d u r e that has b e e n d e s c r i b e d and e v a l u a t e d p r e v i o u s l y (9, i0). The solvent b l a n k was g e n e r a l l y < i 0 p g / t u b e and has not b e e n deducted. The i n t e r a s s a y r e c o v e r y of cortisol f r o m a 2 . 5 ng/ml p l a s m a p o o l was 2.56 ~ 0.32 ng/ml (~ SD, n = ii). P r o g e s t e r o n e a n d e s t r a d i o l w e r e m e a s u r e d b y radioi m m u n o a s s a y (ii). The mean (~ SD) solvent blanks w e r e e q u i v a l e n t to 0.03 + 0.03 ng/ml and 2.4 + 3.8 p g / m l respectively. The i n t ë r a s s a y r e c o v e r i e s (mëan ~ SD) of p r o g e s t e r o n e f r o m a 0.5 ng/ml pool, and of e s t r a d i o l from a 2 5 0 p g / m l p o o l w e r e 0.46 ~ 0.07 ng/ml and 244 ~ 31 p g / m l
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(n = 6 and 14) r e s p e c t i v e l y . P r o s t a g l a n d i n F and PGE w e r e m e a s u r e d after their s e p a r a t i o n by silicic acid c h r o m a t o g r a p h y u s i n g a p r e v i o u s ly d e s c r i b e d and e v a l u a t e d p r o c e d u r e (12, 13). Characteriz a t i o n of PGF's or PGE's other than group s e p a r a t i o n was not attempted, a n d the results are e x p r e s s e d as PGF»~ or PGE 2 e q u i v a l e n t s S o l v e n t b l a n k s for b o t h p r o s t a g l ä ~ d i n s w e r e less than 5 " p g / t u b e and h a v e not b e e n deducted. The c o e f f i c i e n t s of v a r i a t i o n for PGE and p G F at mean conc e n t r a t i o n s of 47 a n d 38 p g / m l were 8 . 9 % and 11.7% respectively. The mean c o n c e n t r a t i o n s of P G E and PGF in the p e r i p h e r a l p l a s m a of n o n - p r e g n a n t sheep w e r e 123 + 45 pg/ml and 23 ~ 17 p g / m l (n = 12, b o t h ~ SD) respectivel~. In v i e w of the d e m o n s t r a t i o n that adult sheep b l o o d c o n t a i n s a p r o s t a g l a n d i n - 9 keto r e d u c t a s e e n z y m e (14) the p o s s i b i l i t y was e x a m i n e d that such an enzyme in fetal b l o o d c o u l d alter the c o n c e n t r a t i o n s of PGE ~ d PGF that w e r e subsequently determined. Fetal and m a t e r n a % b l o o d w e r e incubared w i t h p u r i f i e d ~ , 6 , 8 , 1 1 , 1 2 , 1 4 , 1 5 ( n ) - J H ] PGE 9 (specific ac~ivity, 140 Ci/mmole; R a d i o c h e m i c a l Centre, A m e r s h a m ) aZ 37vC and 4 U C for 15, 30, 45 or 60 min. No c o - f a c t o r s were a d d e d and the gaseous p h a s e was air; i.e. the b l o o d was inc u b a t e d under c o n d i t i o n s similar to those p r e v a i l i n g d u r i n g the time of sample c o l l e c t i o n . After the v a r i o u s time intervals, the i n c u b a t e s were i m m e d i a t e l y a c i d i f i e d a n d ext r a c t e d w i t h 2 x 5 volumes ethyl acetate. The extracts w e r e c h r o m a t o g r a p h e d on t.l.c. ( c h l o r o f o r m : m e t h a n o l : a c e t i c a c i d : w a t e r , 9 0 : 8 : 1 : 0 . 8 , v/v) a n d the r a d i o a c t i v i t y was l o c a t e d using a B e r t h o l d r a d i o c h r o m a t o g r a m scanner. A f t e r i n c u b a t i o n o f ~2H ]_P G_E w i t h b o t h maternal a n d fetal b l o o d for 1 h at 37°C, some r a d i o a c t i v i t y (approx.1020%) was l o c a t e d in the zone c o r r e s p o n d i n g to PGF~ (R~ = 0.18), a l t h o u g h this was not p u r i f i e d further. However, after only 15 min aZ b o t h 37°C a n d 4°C, g r e a t e r than 95% of the r a d i o a c t i v i t y c o - c h r o m a t o g r a p h e d with PGE 2 (R• = 0.54). B e c a u s e the time b e t w e e n sample c o l l e c t i o n an~ c e ~ t r i f u g a t i o n was g e n e r a l l y less than this interval, it was felt that b l o o d m e t a b o l i s m of PGE 2 to PGF~ w o u l d be u n l i k e l y to i n t r o d u c e large errors into the s u b ~ ~ q u e n t m e a s u r e m e n t s . RESULTS Outcome
of Pregnancy.
The length of g e s t a t i o n in the 5 sheep r a n g e d b e t w e e n 141 and 144 days. Four animals gave b i r t h to viable lambs with b i r t h w e i g h t s ranging f r o m 2.37 - 4.56 Kg. One sheep (ewe 106) gare b i r t h to triplets, one live, and Zwo, i n c l u d i n g the c a t h e % e r i z e d fetus, stillborn. This fetus d i e d w i t h i n the 24 h p r e c e d i n g p a r t u r i t i o n , a l t h o u g h its c o n d i t i o n h a d d e t e r i o r a t e d g r a d u a l l y over the p r e v i o u s 12 days as j u d g e d
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f r o m a 9radual fall in p0^ (18 mm Hg on day 127 to 9 mm Hg on day 139), an e l e v a t e d ~ C O 9 ( > 50 mm. Hg), and b a s a l cortisol levels of 50-100 ngTml. Blood Gas a n d Hormone
Concentrations.
The q u a l i t a t i v e changes in fetal p l a s m a p r o s t a g l a n d i n c o n c e n t r a t i o n s were similar in the fetus of ewe i06 to the other fetuses» i r r e s p e c t i v e of whether the fetal catheter was i m p l a n t e d into the femoral artery or jugular rein. The mean values for all 5 animals are p r e s e n t e d in Fig. i. There was no s i g n i f i c a n t change ~ the mean fetal b l o o d pH, p O p or p C O 2 throughout the latter pari of gestation in the ~our fetuses with femoral a r t e r y catheters. However, on the day of p a r t u r i t i o n , and i m m e d i a t e l y p o s t p a r t u m ±here was a consistent fall in the m e a n pH, and an i n c r e a s e in p C O o. Similar changes have b e e n r e p o r t e d b y other i n v e s t i g a t o r s (~5). The mean fetal p l a s m a cortisol c o n c e n t r a t i o n i n c r e a s e d s i g n i f i c a n t l y from values of less than 20 ng/ml up to i0 days pre partum» to c o n c e n t r a t i o n s in excess of 200 ng/ml on the two days preceding» and the day of p a r t u r i t i o n (P < 0.001). There w a s a further increase in the mean cortisol c o n c e n t r a t i o n i m m e d i a t e l y after parturition» which was just s t a t i s t i c a l l y s i g n i f i c a n t (P < 0.05). Of the 2 p r i m a r y p r o s t a g l a n d i n s s the mean fetal p l a s m a levels of PGE w e r e c o n s i s t e n t l y hlgher than PGF. The ratio b e t w e e n the mean values during the time intervals i n d i c a t e d in Fig. 1 v a r i e d f r o m 1.16 to a value of 3.54 on the day of parturition. This increase in the ratio of PGE:PGF immediateiy before d e l i v e r y largely r e f l e c t e d a rise in the mean PGE concentration. The mean c o n c e n % r a t i o n o f P G E during the last 24 h of p r e g n a n c y was s i g n i f i c a n t l y greater %han at any other ~ m e (P < 0.005). The mean PGE c o n c e n t r a t i o n d e c r e a s e d s i g n i f i c a n t l y in samples taken f r o m n e w b o r n lambs w i t h i n 2 h of d e l i v e r y (P < 0.025). In contrast to the change in fetal p l a s m a P G E s there was no s i g n i f i c a n t change in the fetal p l a s m a c o n c e n t r a t i o n of PGF during the latter p a r i of g e s t a t i o n (Fig.l). R e l a t i o n s h i p b e t w e e n fetal a n d u t e r o - o v a r i a n @landin concentrations.
vein prosta-
We, and others, have p r e v i o u s l y d o c u m e n t e d a 20-50 fold increase in the c o n c e n t r a t i o n of PGF in the uteroovarian rein of sheep during the final 12-24 h of p r e g n a n c y (see 7 a n d 16). Three sheep w e r e therefore p r e p a r e d w i t h c a t h e t e r s i m p l a n t e d in a main u t e r o - o v a r i a n vein in order to relate more closely the changes in p r o s t a g l a n d i n concentrations in this vessel to /hose in the fetal plasma. The
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r e s u l t s for 2 a n d 3.
two r e p r e s e n t a t i v e
animals
are
shown
in Figs.
In both sheep the increase in the ooncentration of fetal cortisol and maternal estradiol, and the decrease in maternal progesterone characteristic of normal parturition was noted. In both £etuses, ~asma samples taken wi~in 24 h of parturition showed a clear increase in the PGE concentration, but little change in PGF. This was in contrast to the changes in the maternal utero-ovarian vein, where the concentration of PGF increased by a factor of i0 or more, w h i l e P G E s h o w e d l i t t l e (no. 79) or no (no. 96) change. A f t e r p a r t u r i t i o n , the c o n c e n t r a t i o n of b o t h p r o s t a g l a n d i n s in the p l a s m a of the n e w b o r n l a m b s f e l l r a p i d l y , c o m p a r e d to the l e v e l s f o u n d in t h e s e s a m e a n i m a l s as f e t u s e s a f e w h o u r s p r e v i o u s l y . In the f e t u s of ewe no. 79, the c o n c e n t r a t i o n of P G E in f e t a l p l a s m a was e l e v a t e d b e t w e e n d a y s 1 2 4 - 1 3 4 of p r e g nancy. No o b v i o u s e x p l a n a t i o n on the b a s i s o f the o t h e r p a r a m e t e r s t h a t w e r e m e a s u r e d c a n be o f f e r e d for t h i s f i n d i n g , a n d this w a s the o n l y f e t u s to s h o w s u c h c h a n g e s . DISCUSSION The p r e s e n t m e a s u r e m e n t s s h o w that d u r i n g laie p r e g n a n c y , the m e a n c o n c e n t r a t i o n of P G E in f e m o r a l a r t e r i a l or j u g u l a r v e n o u s p l a s m a of the f e t a l l a m b is g r e a t e r t h a n t h a t of PGF. D u r i n g the final 1 2 - 2 4 h o f g e s t a t i o n , the c o n c e n t r a t i o n of P G E i n c r e a s e s , w h i l s t P G F c h a n g e s l i t t l e . T h i s is in c o n t r a s t to the l a r g e i n c r e a s e in P G F a n d v a r i a b l e c h a n g e in P G E f o u n d in the m a t e r n a l u t e r o - o v a r i a n v e i n at this time. The r a t i o o f P G E : P G F in f e t a l p l a s m a c o u l d be of i m p o r t a n c e in r e l a t i o n t o the p a t e n c y of the d u c t u s a r t e ~ o sus. In v i t r o e x p e r i m e n t s h a v e s h o w n t h a t E p r o s t a g l a n d i n s d i l a t e , a n d F p r o s t a g l a n d i n s e o n s t r i c t the d u c t u s (2, 3). In a d d i t i o n , a d m i n i s t r a t i o n of i n d o m e t h a c i n to p r e g n a n t e w e s m a y r e s u l t in p r e m a t u r e c l o s u r e of the d u c t u s a r t e r i o s u s in u t e r o (4). W h i l s t t h e s e d a t a i m p l i c a t e p r o s t a g l a n d i n s in the m a i n t e n a n c e of d u c t a l p a t e n c y , it is not yet k n o w n w h e t h e r t h e i r a c t i o n is due to c i r c u l a t i n g p r o s t a g l a n d i n s or to loca] p r o s t a g l a n d i n p r o d u c t i o n w i t h i n the v e s s e l . A c o n s i s t e n t f i n d i n g in all the f e t u s e s s t u d i e d was an i n c r e a s e in the c o n c e n t r a t i o n of P G E in s a m p l e s of f e t a l p l a s m a t a k e n w i t h i n 24 h of d e l i v e r y . However the f a c t o r s r e s p o n s i b l e f o r t h i s i n c r e a s e a n d its s i g n i f i c a n c e to the f e t u s are n o t k n o w n . It a p p e a r s to be f e t a l in o r i g i n , b e c a u s e t h e r e is no c o m p a r a b l e c h a n g e in the u t e r o - o v a r i a n P G R concentration. In the p r e s e n t s t u d y ~ no o b v i o u s r e l a t i o n s h i p b e t w e e n f e t a l p l a s m a p r o s t a g l a n d i n l e v e l s a n d the b l o o d
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gas status of The feTus was apparenT, alThough The increase in feTal PGE at Term does occur at a Time when The mean pCO_ is increasmng, and pO~ ms fallmng. OTher aspecTs of feTal physmology, mnclud•ng feTal b r e a T h m n g also change at Thls Time (17), and The relaTionship of these changes To feTal p r o s T a g l a n d i n levels are currenTly under invesTigation. •
°
•
~
.
°
After parturiTion, there was a rapid decrease in The c o n c e n T r a T i o n of PGE, and To a lesser extent PGF, in The p l a s m a of The newborn. This is consisTenT wiTh the observaTion ThaT The lungs of The feTal lamb, as of the feßal rabbit (18) conTain The p r o s T a g l a n d i n 15-hydroxy dehydrogenase and reducTase systems (M.J.N.C. Keirse» p e r s o n a l communicaTion). During inTra-uTerine life, b l o o d flow To the fetal lung is o n l y abouT 5 - 1 0 % of cardiac outpuT (8), which may explain w h y The c o n c e n T r a T i o n of p r i m a r y prosTaglandins is higher in The fetus Than in The adulT. After birTh, as The lungs expand and Their b l o o d flow increases, it seems likely ThaT c i r c u l a T i n g p r o s T a g l a n d i n s are meTab o l i s e d more rapidly and Their c o n c e n T r a T i o n falls. This study raises a number of questions wiZh respect to the sites of p r o d u c t i o n and action of p r i m a r y prostaglandins in the fetus. It indicates that studies implicaring p r o s t a g l a n d i n s as regulators of p l a c e n t a l b l o o d flow, fetal b l o o d p r e s s u r e (i) and ductal pa%ency(2-5) may have a sound p h y s i o l o g i c a l basis. In v i e w of the suggested use of p r o s t a g l a n d i n synThetase inhibiTors in The management of B h r e a t e n e d p r e m a T u r e labour (19), it w o u l d seem desirable To u n d e r s T a n d more deeply the funcTions ~ d imporTance of p r o s T a g l a n d i n s in The feTus.
REFERENCES. i.
Novy, M.J., Piasecki, G., Jackson, B.T. (1974). Effect of p r o s t a g l a n d i n s E~ and F2~ on umbilical b l o o d flow and fetal hemodynam[cs. Pro~taßlandins, ~, 543-555.
2.
Starling, M.B. & Elliott, R.B. (1974). The effects of p r o s t a g l a n d i n s , p r o s t a g l a n d i n inhibitors, and oxygen on the closure of the ductus arteriosus, p u l m o n a r y arteries and umbilical vessels in vitro. P r o s t a ~ l a n d i n s , ~, 187-203.
3.
Coceani, F., Olley, P.M., & Bodach, E. (1975).Lamb ductus arteriosus: effect of p r o s t a g l a n d i n synthesis inhibitors on the muscle tone and the response to p r o s t a g l a n d i n E 2. Prostaßlandins, ~, 299-308.
4.
Coceani, F., Olley, P.M. & Bodach, E. (1975).Prostaglandins: a p o s s i b l e regulator of muscle tone in the ductus arteriosus. Proc. Int. Conf. Prostaglandins, Florence, 1975 p.151 (abstr.).
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PROSTAGLANDINS
5.
Sharpe, G.L., Thalme, B. & Larsson, K.S. (1974). S%udies on closure of the ductus arZeriosus, xi. ductal closure in uZero by a prostaglandin syn%hetase inhibitor. Prostaßlandins» ~, 363-368.
6.
Karim» S.M.M. & Hillier» K. (1975).Physiological roles and pharmacolo9ical ac%ions of prosZaglandins in relation to human reproduction. In P r o s t a g l a n ~ n s and ReproducZion, Ed. Karim, S.M.M., M.T.P., Lancaster, U.K., pp 23-75.
7.
Ligginss G.C., Fairclough, R.J., Grieves, S.A., Kendall, J.Z. & Knox, B.S. (1973).Mechanism of initiation of parturi%ion in the ewe. EecenZ Pro~ress in Hormone Research, 29, 111-150.
8.
Dawes, G.S. (1969) Foetal and Neonatal Physiolo~y. Year Book Medical, Chicago.
9.
Fencl, M. & Tulchinsky, D. (1975). Concentrations of cortisol in amnioZic fluid during pregnancy. New En@l. J. Med., 292, 133-136.
iO.
Challis~ J.E.G., Davies~ I.J., Benirschke, K., Hendrickx, A.G. & Ryan, K.J. (1975). The effecZs dexamethasone on the peripheral plasma concentrations of androstenedione, testosterone and cortisol in the pregnant rhesus monkey. Endocrinologys 96, 185-192.
ii.
Challis, J.R.G., Davies, I.J., & •yan, K.J. (1973). The concentraZion of progesterone, estrone and esZradiol-17~ in the plasma of pregnant rabbits. Endocrinolog~ , 93, 971-976.
12.
Hillier, K. & DilIey,S.R. (1974). Separation and radioimmunoassay of F prosZaglandins using silica gel micro columns. Prostag~andins , ~, 137-150.
13.
Challis, J.R.G., Calder, A.A., Dilley, S., Forster, C.S.~ Hillier, K., HunZer 3 D.J.S., MacKenzie, I.Z. & Thorburn G.D. ( 9 7 6 ) . Production of prostaglandin E and F by corpora luZea, corpora albicantes and sZroma fro~ Zhe human ovary. J. Endocr. 68 (in press).
14.
Hensby, C.N. (1974).Reduction of prosZaglandin E 2 to prostaglandin F_ by an enzyme in sheep blood° Biochim Biophys~~cta~ 348, 145-154.
15.
Comline, R.S. & Silver, M. (1972).The composition of foetal and maZernal blood during parturition in the ewe. J. Physiol (Lond.)272, 233-256.
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16.
Challis, J.R.G. & Thorburn,G.D. (1975).Prenatal endocrine function and the initiation of parturition. Br°Med. Bull., 31» 57-62.
17.
Boddy, K. & Dawes, G.S. Br.Med. Bull.~ 31, 3-7.
18.
Sun, F.F., & Armour, S.B. (1974).Prosta91andin 15hydroxy dehydrogenase and ~13 reductase levels in the lungs of maternal, fetal and neonatal rabbits. Prostaßlandins, Z, 327-338.
19.
Zuckerman, ~~ Reiss, U., & Rubinstein, I. (1974). Inhibition of human premature labor by indomethacin. Obstet. Gynecol., 44, 787-792.
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(1975).Fetal breathing.
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PROSTAGLANDINS
7.3 pH 7.2 7.1 60 pCO2 [ ]
m
Z
40
~
J.
po2 E3 (mm Hg)
20 0 600
PGFtt
(pglml)
4O0 200
i tIt:l:lIiI[~
0 800
PGE
600
(pglml) 400 200
0 4O0
300 CORTISOL
(nglml)
200 IO0 0
40
30
2)
20
15
10
5
0 PP
DAYS BEFORE PARTURITION
F I G U R E i. T h e c o n c e n t r a ± i o n s ~ cortisol, PGE & PGF a n d the b l o o d gas a n d p H s t a t u s in c h r o n i c a l l y c a t h e t e r i z e d f e t a l l a m b s d u r i n g the last 35 days of p r e g n a n c y . C o r t i s o l & P G v a l u e s are the m e a n + $ . E . M . of 5 - 1 6 obs e r v a t i o n s on 5 f e t u s e s . B l o o d g a s e ß are the m e a n + S.E.M. o f 4 - 1 5 o b s e r v a t i o n s on the 4 of t h e s e f e t u s e s w h ~ c h h a d f e m o r a l a z t e r y c a t h e t e r s . T h e d a y of p a r t u r i t i o n has b e e n t a k e n as d a y 0. PP~ p o s t p a r % u m .
1050
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VOL. 11 NO. 6
PROSTAGLANDINS
EWE 96 NORMAL PREGNANCY ~ 4
~
A
E
l=
PART'N
1600
~ . i,u Z
Z
800 Lu~~
~°°
g 0 (7226) ,t~ I I
1600 E
E
i
I
800
I
I I
~j...X
-
0300[-
'°o°of_ J
E >.~,
Ob
80
(85)
(88)
• o zm r=
~O
v
~»_o
40
0 124
128
132
136
140
144
148
OAYS OF PREGNANCY
F I G U R E 2. H o r m o n e c h a n g e s i n ovarian venous plasma in ewe pregnancy and parturition.
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fetal and 96 during
uterolate
1051
PROSTAGLANDINS
EWE a 4 ==
79 NORMAL
PREGNANCY
108
112
116
120
DAYS
FIGURE 3. Hormone changes ovarian venous plasma in pregnancy and parturition.
1052
PART'N
1600
OF
124
128
132
136
140
PREGNANCY
in ewe
fetal and 79 during
uterolate
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PROSTAGLANDINS
J.R.G.
Challis,
S.R.
IN THE C I R C U L A T I O N
Dilley,
J.S.
OF THE FETAL LAMB
Robinson,
G.D.
Thorburn
U n i v e r s i t y of Oxford, N u f f i e l d Institute for M e d i c a l Research, John Radcliffe Hospital, D e p a r t m e n t of O b s t e t r i c s & Gynaecology, H e a d l e y Way, Headington, Oxford.
ABSTRACT P r o s t a g l a n d i n E and PGF have b e e n m e a s u r e d in the p l a s m a of c h r o n i c a l l y c a t h e t e r i z e d fetal lambs throughout the last 20-35 days (0.73 onwards) of gestation. The m e a n c o n c e n t r a t i o n of PGE was higher than that of PGF. There was a s i g n i f i c a n t increase in the c o n c e n t r a t i o n of PGE but little change in the c o n c e n t r a t i o n of PGF in samples of fetal plasma taken w i t h i n 24 h of parturition. In contrast, at this time in m a t e r n a l u t e r o - o v a r i a n venous plasma, there was a large increase in PGF, but r e l a t i v e l y little change in PGE. There was a s i g n i f i c a n t d e c r e a s e in the c o n c e n t r a t i o n of PGE and PGF in the plasma of lambs w i t h i n 12 h after b i r t h compared to the levels found in the same animals as fetuses a few hours previously. The p h y s i o l o g i c a l importance of these changes is discussed.
ACKNOWLEDGEMENTS We thank Mr. A. Stevens, Ms. C. Forster, G. Pooley, P. H a r t l e y and Mrs. L. C l o v e r for their e x c e l l e n t technical assistance, and Drs. J. Hennam, B.J.A. Furr, and May & Baker Ltd. for g e n e r o u s l y supplying antibodies. The w o r k was s u p p o r t e d by an M.R.C. Grant.
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PROSTAGLANDINS
INTRODUCTION Recent studies h a v e s u g g e s t e d that p r o s t a g l a n d i n s may be i n v o l v e d in v a r i o u s aspects of fetal p h y s i o l o g y . The i n f u s i o n of PGE 2 into fetal lambs r e s u l t e d in c a r d i o v a s cular changes in the fetal c i r c u l a t i o n and p l a c e n t a l b e d (i). In addition, d i f f e r e n t p r o s t a g l a n d i n s may e i t h e r c o n s t r i c t or dilate the ductus a r t e r i o s u s of fetal lambs and fetal calves in vitro (2, 3), and the a d m i n i s t r a t i o n of i n d o m e t h a c i n to ewes (4) or rats (5) during late pregnancy provoked p r e m a t u r e c losure ~ the ductus a r t e r i o s u s in utero i m p l y i n g that p r o s t a g l a n d i n s were i n v o l v e d in m a i n t a i n i n g the p a t e n c y of this vessel. D e s p i t e the a p p a r e n t i m p o r t a n c e of p r o s t a g l a n d i n s in the fetus, e s t i m a t e s of p r i m a r y p r o s t a g l a n d i n s have b e e n r e s t r i c t e d largely to m e a s u r e m e n t s of their c o n c e n t r a t i o n s in a m n i o t i c f l u i d or u m b i l i c a l cord p l a s m a (see 6). These e s t i m a t e s h a v e o r t e n b e e n on single rather than serial samples. However, the d e v e l o p m e n t of procedures for imp l a n t i n g and m a i n t a i n i n g v a s c u l a r c a t h e t e r s in fetal lambs t h r o u g h o u t laie p r e g n a n c y p e r m i t s b l o o d samples to be taken s e r i a l l y f r o m the c o n s c i o u s fetus in utero. U s i n g this p r e p a r a t i o n , the p r e s e n t study was d - ë s ~ n e d to measure the c o n c e n t r a t i o n s of PGE a n d P G F in serial samples of fetal plasma. We w i s h e d to e s t a b l i s h w h e t h e r the p r o s t a g l a n d i n levels c h a n g e d during p r e g n a n c y , p a r t i c u l a r l y in r e l a t i o n to p a r t u r i t i o n , w h e n the c o n c e n t r a t i o n o f PGF in the u t e r o - o v a r i a n vein is k n o w n to rise (see 7), and after birth, as p u l m o n a r y b l o o d flow i n c r e a s e s in the n e w b o r n (8). MATERIALS
AND M E T H O D S
Animals The live sheep u s e d in these e x p e r i m e n t s were Border L e i c e s t e r x S u f f o l k cross. The day of marking by an intact ram was taken as day zero of p r e g n a n c y . Fetal c a t h e t e r s were i m p l a n t e d u n d e r c o n d i t i o n s of strict asepsis b e t w e e n days 106-126 of p r e g n a n c y . The ewes w e r e a n a e s t h e t i z e d w i t h t h i o p e n t o n e (i g i.v.), and maint a i n e d w i t h f l u o t h a n e a n d oxygen. The uterus was e x p o s e d by a m i d - l i n e s u b - u m i l i c a l incision, and in four of the animals the fetal h i n d limb was l o c a t e d and e x p o s e d b y a small i n c i s i o n through the ußerine wall. Loss of a m n i o t i c f l u i d was p r e v e n t e d u s i n g Allis forceps to clip the skin to the u t e r i n e wall. A c a t h e t e r (PP 90 i.d. 0.86 mm., o.d. i.i mm., Portex) was i n s e r t e d into a f e m o r a l artery, such that its tip lay in the dorsal aorta. The c a t h e t e r was
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PROSTAGLANDINS
s u Z u r e d Zo The skin» Zhe fetal limb replaced» and Zhe a m n i o t i c sac and u Z e r u s c l o s e d in a single layer. In the f i f Z h animal Zhe feZal h e a d was l o c a Z e d a n d e x p o s e d , a n d a c a Z h e Z e r (PP 90, PorZex) was i n s e r Z e d inZo a fe±al jugular rein. The feZal c a Z h e Z e r s w e r e e x Z e r i o r i z e d Zhrough a small f l a n k incision, a n d f i l l e d w i Z h sZerile h e p a r i n saline (500 uniZs/ml). In Zhree of Zhe animals a sofZ vinyl c a Z h e Z e r (i.d. 1.0 mm., o.d. 1.5 mm.» Dural PlasZics) was imp l a n Z e d inZo a main u Z e r o - o v a r i a n vein Z h r o u g h a small ZribuZary» and e x Z e r i o r i z e d Zhrough Zhe flank of Zhe ewe. Vinyl c a Z h e Z e r s (sofZ vinyl 4, PorZex, i.d. 2 mm.) were i n s e r Z e d inZo a m a Z e r n a l c a r o Z i d arZery and exZernal j u g u l a r vein. All Zhese c a Z h e Z e r s w e r e f l u s h e d and f i l l e d w i Z h h e p a r i n - saline (500 uniZs/ml). B l o o d samples (i0 ml. f r o m the maternal vessels; 6 ml. f r o m the fetal vessels) were drawn e v e r y other day inZo h e p a r i n i z e d syringes, and Z r a n s f e r r e d i m m e d i a Z e l y Zo c h i l l e d Zube~. The b l o o d was c e n Z r i f u g e d i m m e d i a Z e l y aZ 2000 x g aZ 4 C for 15 min A a n d Zhe p l a s m a was d i v i d e d inZo aliquoZs a n d s Z o r e d aZ - 2 0 - C unZil assayed. B l o o d samples (i ml) for b l o o d gas and p H a n a l y s e s w e r e c o l l e c Z e d ~ sZerile h e p a r i n i z e d glass syringes. In order to e s t a b l i s h b a s e line v a l u e s for the conc e n t r a t i o n of p r i m a r y ~rostaglandins in the ~ a s m a of adult sheep» samples w e r e ±aken by v e n e p u n c t u r e f r o m the jugular r e i n of 12 n o n - p r e g n a n t ewes at r a n d o m stages of the o e s t r o u s cycle. The b l o o d was c o l l e c t e d into h e p a r i n i z e d syringes, t r a n s f e r r e d to c h i l l e d tubes, and immediately c e n t r i f u g e d at 2000 x g for 15 min. The p l a s m a was d i v i d e d into aliquoßs, a n d s t o r e d at - 2 0 ° C until assayed. B l o o d Gas M e a s u r e m e n ± s . The P02, p C O 2 and p H of the maternal a n d fetal b l o o d samples were m e a s ü r e d u s i n g a R a d i o m e t e r Model 27. Haematocrits w e r e m e a s u r e d u s i n g a micro c e n t r i f u g a t i o n procedure. Radioimmunoassay. C o r t i s o l was m e a s u r e d by a r a d i o i m m u n o a s s a y p r o c e d u r e that has b e e n d e s c r i b e d and e v a l u a t e d p r e v i o u s l y (9, i0). The solvent b l a n k was g e n e r a l l y < i 0 p g / t u b e and has not b e e n deducted. The i n t e r a s s a y r e c o v e r y of cortisol f r o m a 2 . 5 ng/ml p l a s m a p o o l was 2.56 ~ 0.32 ng/ml (~ SD, n = ii). P r o g e s t e r o n e a n d e s t r a d i o l w e r e m e a s u r e d b y radioi m m u n o a s s a y (ii). The mean (~ SD) solvent blanks w e r e e q u i v a l e n t to 0.03 + 0.03 ng/ml and 2.4 + 3.8 p g / m l respectively. The i n t ë r a s s a y r e c o v e r i e s (mëan ~ SD) of p r o g e s t e r o n e f r o m a 0.5 ng/ml pool, and of e s t r a d i o l from a 2 5 0 p g / m l p o o l w e r e 0.46 ~ 0.07 ng/ml and 244 ~ 31 p g / m l
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PROSTAGLANDINS
(n = 6 and 14) r e s p e c t i v e l y . P r o s t a g l a n d i n F and PGE w e r e m e a s u r e d after their s e p a r a t i o n by silicic acid c h r o m a t o g r a p h y u s i n g a p r e v i o u s ly d e s c r i b e d and e v a l u a t e d p r o c e d u r e (12, 13). Characteriz a t i o n of PGF's or PGE's other than group s e p a r a t i o n was not attempted, a n d the results are e x p r e s s e d as PGF»~ or PGE 2 e q u i v a l e n t s S o l v e n t b l a n k s for b o t h p r o s t a g l ä ~ d i n s w e r e less than 5 " p g / t u b e and h a v e not b e e n deducted. The c o e f f i c i e n t s of v a r i a t i o n for PGE and p G F at mean conc e n t r a t i o n s of 47 a n d 38 p g / m l were 8 . 9 % and 11.7% respectively. The mean c o n c e n t r a t i o n s of P G E and PGF in the p e r i p h e r a l p l a s m a of n o n - p r e g n a n t sheep w e r e 123 + 45 pg/ml and 23 ~ 17 p g / m l (n = 12, b o t h ~ SD) respectivel~. In v i e w of the d e m o n s t r a t i o n that adult sheep b l o o d c o n t a i n s a p r o s t a g l a n d i n - 9 keto r e d u c t a s e e n z y m e (14) the p o s s i b i l i t y was e x a m i n e d that such an enzyme in fetal b l o o d c o u l d alter the c o n c e n t r a t i o n s of PGE ~ d PGF that w e r e subsequently determined. Fetal and m a t e r n a % b l o o d w e r e incubared w i t h p u r i f i e d ~ , 6 , 8 , 1 1 , 1 2 , 1 4 , 1 5 ( n ) - J H ] PGE 9 (specific ac~ivity, 140 Ci/mmole; R a d i o c h e m i c a l Centre, A m e r s h a m ) aZ 37vC and 4 U C for 15, 30, 45 or 60 min. No c o - f a c t o r s were a d d e d and the gaseous p h a s e was air; i.e. the b l o o d was inc u b a t e d under c o n d i t i o n s similar to those p r e v a i l i n g d u r i n g the time of sample c o l l e c t i o n . After the v a r i o u s time intervals, the i n c u b a t e s were i m m e d i a t e l y a c i d i f i e d a n d ext r a c t e d w i t h 2 x 5 volumes ethyl acetate. The extracts w e r e c h r o m a t o g r a p h e d on t.l.c. ( c h l o r o f o r m : m e t h a n o l : a c e t i c a c i d : w a t e r , 9 0 : 8 : 1 : 0 . 8 , v/v) a n d the r a d i o a c t i v i t y was l o c a t e d using a B e r t h o l d r a d i o c h r o m a t o g r a m scanner. A f t e r i n c u b a t i o n o f ~2H ]_P G_E w i t h b o t h maternal a n d fetal b l o o d for 1 h at 37°C, some r a d i o a c t i v i t y (approx.1020%) was l o c a t e d in the zone c o r r e s p o n d i n g to PGF~ (R~ = 0.18), a l t h o u g h this was not p u r i f i e d further. However, after only 15 min aZ b o t h 37°C a n d 4°C, g r e a t e r than 95% of the r a d i o a c t i v i t y c o - c h r o m a t o g r a p h e d with PGE 2 (R• = 0.54). B e c a u s e the time b e t w e e n sample c o l l e c t i o n an~ c e ~ t r i f u g a t i o n was g e n e r a l l y less than this interval, it was felt that b l o o d m e t a b o l i s m of PGE 2 to PGF~ w o u l d be u n l i k e l y to i n t r o d u c e large errors into the s u b ~ ~ q u e n t m e a s u r e m e n t s . RESULTS Outcome
of Pregnancy.
The length of g e s t a t i o n in the 5 sheep r a n g e d b e t w e e n 141 and 144 days. Four animals gave b i r t h to viable lambs with b i r t h w e i g h t s ranging f r o m 2.37 - 4.56 Kg. One sheep (ewe 106) gare b i r t h to triplets, one live, and Zwo, i n c l u d i n g the c a t h e % e r i z e d fetus, stillborn. This fetus d i e d w i t h i n the 24 h p r e c e d i n g p a r t u r i t i o n , a l t h o u g h its c o n d i t i o n h a d d e t e r i o r a t e d g r a d u a l l y over the p r e v i o u s 12 days as j u d g e d
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PROSTAGLANDINS
f r o m a 9radual fall in p0^ (18 mm Hg on day 127 to 9 mm Hg on day 139), an e l e v a t e d ~ C O 9 ( > 50 mm. Hg), and b a s a l cortisol levels of 50-100 ngTml. Blood Gas a n d Hormone
Concentrations.
The q u a l i t a t i v e changes in fetal p l a s m a p r o s t a g l a n d i n c o n c e n t r a t i o n s were similar in the fetus of ewe i06 to the other fetuses» i r r e s p e c t i v e of whether the fetal catheter was i m p l a n t e d into the femoral artery or jugular rein. The mean values for all 5 animals are p r e s e n t e d in Fig. i. There was no s i g n i f i c a n t change ~ the mean fetal b l o o d pH, p O p or p C O 2 throughout the latter pari of gestation in the ~our fetuses with femoral a r t e r y catheters. However, on the day of p a r t u r i t i o n , and i m m e d i a t e l y p o s t p a r t u m ±here was a consistent fall in the m e a n pH, and an i n c r e a s e in p C O o. Similar changes have b e e n r e p o r t e d b y other i n v e s t i g a t o r s (~5). The mean fetal p l a s m a cortisol c o n c e n t r a t i o n i n c r e a s e d s i g n i f i c a n t l y from values of less than 20 ng/ml up to i0 days pre partum» to c o n c e n t r a t i o n s in excess of 200 ng/ml on the two days preceding» and the day of p a r t u r i t i o n (P < 0.001). There w a s a further increase in the mean cortisol c o n c e n t r a t i o n i m m e d i a t e l y after parturition» which was just s t a t i s t i c a l l y s i g n i f i c a n t (P < 0.05). Of the 2 p r i m a r y p r o s t a g l a n d i n s s the mean fetal p l a s m a levels of PGE w e r e c o n s i s t e n t l y hlgher than PGF. The ratio b e t w e e n the mean values during the time intervals i n d i c a t e d in Fig. 1 v a r i e d f r o m 1.16 to a value of 3.54 on the day of parturition. This increase in the ratio of PGE:PGF immediateiy before d e l i v e r y largely r e f l e c t e d a rise in the mean PGE concentration. The mean c o n c e n % r a t i o n o f P G E during the last 24 h of p r e g n a n c y was s i g n i f i c a n t l y greater %han at any other ~ m e (P < 0.005). The mean PGE c o n c e n t r a t i o n d e c r e a s e d s i g n i f i c a n t l y in samples taken f r o m n e w b o r n lambs w i t h i n 2 h of d e l i v e r y (P < 0.025). In contrast to the change in fetal p l a s m a P G E s there was no s i g n i f i c a n t change in the fetal p l a s m a c o n c e n t r a t i o n of PGF during the latter p a r i of g e s t a t i o n (Fig.l). R e l a t i o n s h i p b e t w e e n fetal a n d u t e r o - o v a r i a n @landin concentrations.
vein prosta-
We, and others, have p r e v i o u s l y d o c u m e n t e d a 20-50 fold increase in the c o n c e n t r a t i o n of PGF in the uteroovarian rein of sheep during the final 12-24 h of p r e g n a n c y (see 7 a n d 16). Three sheep w e r e therefore p r e p a r e d w i t h c a t h e t e r s i m p l a n t e d in a main u t e r o - o v a r i a n vein in order to relate more closely the changes in p r o s t a g l a n d i n concentrations in this vessel to /hose in the fetal plasma. The
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VOL. 11 NO. 6
1045
PROSTAGLANDINS
r e s u l t s for 2 a n d 3.
two r e p r e s e n t a t i v e
animals
are
shown
in Figs.
In both sheep the increase in the ooncentration of fetal cortisol and maternal estradiol, and the decrease in maternal progesterone characteristic of normal parturition was noted. In both £etuses, ~asma samples taken wi~in 24 h of parturition showed a clear increase in the PGE concentration, but little change in PGF. This was in contrast to the changes in the maternal utero-ovarian vein, where the concentration of PGF increased by a factor of i0 or more, w h i l e P G E s h o w e d l i t t l e (no. 79) or no (no. 96) change. A f t e r p a r t u r i t i o n , the c o n c e n t r a t i o n of b o t h p r o s t a g l a n d i n s in the p l a s m a of the n e w b o r n l a m b s f e l l r a p i d l y , c o m p a r e d to the l e v e l s f o u n d in t h e s e s a m e a n i m a l s as f e t u s e s a f e w h o u r s p r e v i o u s l y . In the f e t u s of ewe no. 79, the c o n c e n t r a t i o n of P G E in f e t a l p l a s m a was e l e v a t e d b e t w e e n d a y s 1 2 4 - 1 3 4 of p r e g nancy. No o b v i o u s e x p l a n a t i o n on the b a s i s o f the o t h e r p a r a m e t e r s t h a t w e r e m e a s u r e d c a n be o f f e r e d for t h i s f i n d i n g , a n d this w a s the o n l y f e t u s to s h o w s u c h c h a n g e s . DISCUSSION The p r e s e n t m e a s u r e m e n t s s h o w that d u r i n g laie p r e g n a n c y , the m e a n c o n c e n t r a t i o n of P G E in f e m o r a l a r t e r i a l or j u g u l a r v e n o u s p l a s m a of the f e t a l l a m b is g r e a t e r t h a n t h a t of PGF. D u r i n g the final 1 2 - 2 4 h o f g e s t a t i o n , the c o n c e n t r a t i o n of P G E i n c r e a s e s , w h i l s t P G F c h a n g e s l i t t l e . T h i s is in c o n t r a s t to the l a r g e i n c r e a s e in P G F a n d v a r i a b l e c h a n g e in P G E f o u n d in the m a t e r n a l u t e r o - o v a r i a n v e i n at this time. The r a t i o o f P G E : P G F in f e t a l p l a s m a c o u l d be of i m p o r t a n c e in r e l a t i o n t o the p a t e n c y of the d u c t u s a r t e ~ o sus. In v i t r o e x p e r i m e n t s h a v e s h o w n t h a t E p r o s t a g l a n d i n s d i l a t e , a n d F p r o s t a g l a n d i n s e o n s t r i c t the d u c t u s (2, 3). In a d d i t i o n , a d m i n i s t r a t i o n of i n d o m e t h a c i n to p r e g n a n t e w e s m a y r e s u l t in p r e m a t u r e c l o s u r e of the d u c t u s a r t e r i o s u s in u t e r o (4). W h i l s t t h e s e d a t a i m p l i c a t e p r o s t a g l a n d i n s in the m a i n t e n a n c e of d u c t a l p a t e n c y , it is not yet k n o w n w h e t h e r t h e i r a c t i o n is due to c i r c u l a t i n g p r o s t a g l a n d i n s or to loca] p r o s t a g l a n d i n p r o d u c t i o n w i t h i n the v e s s e l . A c o n s i s t e n t f i n d i n g in all the f e t u s e s s t u d i e d was an i n c r e a s e in the c o n c e n t r a t i o n of P G E in s a m p l e s of f e t a l p l a s m a t a k e n w i t h i n 24 h of d e l i v e r y . However the f a c t o r s r e s p o n s i b l e f o r t h i s i n c r e a s e a n d its s i g n i f i c a n c e to the f e t u s are n o t k n o w n . It a p p e a r s to be f e t a l in o r i g i n , b e c a u s e t h e r e is no c o m p a r a b l e c h a n g e in the u t e r o - o v a r i a n P G R concentration. In the p r e s e n t s t u d y ~ no o b v i o u s r e l a t i o n s h i p b e t w e e n f e t a l p l a s m a p r o s t a g l a n d i n l e v e l s a n d the b l o o d
1046
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PROSTAGLANDINS
gas status of The feTus was apparenT, alThough The increase in feTal PGE at Term does occur at a Time when The mean pCO_ is increasmng, and pO~ ms fallmng. OTher aspecTs of feTal physmology, mnclud•ng feTal b r e a T h m n g also change at Thls Time (17), and The relaTionship of these changes To feTal p r o s T a g l a n d i n levels are currenTly under invesTigation. •
°
•
~
.
°
After parturiTion, there was a rapid decrease in The c o n c e n T r a T i o n of PGE, and To a lesser extent PGF, in The p l a s m a of The newborn. This is consisTenT wiTh the observaTion ThaT The lungs of The feTal lamb, as of the feßal rabbit (18) conTain The p r o s T a g l a n d i n 15-hydroxy dehydrogenase and reducTase systems (M.J.N.C. Keirse» p e r s o n a l communicaTion). During inTra-uTerine life, b l o o d flow To the fetal lung is o n l y abouT 5 - 1 0 % of cardiac outpuT (8), which may explain w h y The c o n c e n T r a T i o n of p r i m a r y prosTaglandins is higher in The fetus Than in The adulT. After birTh, as The lungs expand and Their b l o o d flow increases, it seems likely ThaT c i r c u l a T i n g p r o s T a g l a n d i n s are meTab o l i s e d more rapidly and Their c o n c e n T r a T i o n falls. This study raises a number of questions wiZh respect to the sites of p r o d u c t i o n and action of p r i m a r y prostaglandins in the fetus. It indicates that studies implicaring p r o s t a g l a n d i n s as regulators of p l a c e n t a l b l o o d flow, fetal b l o o d p r e s s u r e (i) and ductal pa%ency(2-5) may have a sound p h y s i o l o g i c a l basis. In v i e w of the suggested use of p r o s t a g l a n d i n synThetase inhibiTors in The management of B h r e a t e n e d p r e m a T u r e labour (19), it w o u l d seem desirable To u n d e r s T a n d more deeply the funcTions ~ d imporTance of p r o s T a g l a n d i n s in The feTus.
REFERENCES. i.
Novy, M.J., Piasecki, G., Jackson, B.T. (1974). Effect of p r o s t a g l a n d i n s E~ and F2~ on umbilical b l o o d flow and fetal hemodynam[cs. Pro~taßlandins, ~, 543-555.
2.
Starling, M.B. & Elliott, R.B. (1974). The effects of p r o s t a g l a n d i n s , p r o s t a g l a n d i n inhibitors, and oxygen on the closure of the ductus arteriosus, p u l m o n a r y arteries and umbilical vessels in vitro. P r o s t a ~ l a n d i n s , ~, 187-203.
3.
Coceani, F., Olley, P.M., & Bodach, E. (1975).Lamb ductus arteriosus: effect of p r o s t a g l a n d i n synthesis inhibitors on the muscle tone and the response to p r o s t a g l a n d i n E 2. Prostaßlandins, ~, 299-308.
4.
Coceani, F., Olley, P.M. & Bodach, E. (1975).Prostaglandins: a p o s s i b l e regulator of muscle tone in the ductus arteriosus. Proc. Int. Conf. Prostaglandins, Florence, 1975 p.151 (abstr.).
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10¢7
PROSTAGLANDINS
5.
Sharpe, G.L., Thalme, B. & Larsson, K.S. (1974). S%udies on closure of the ductus arZeriosus, xi. ductal closure in uZero by a prostaglandin syn%hetase inhibitor. Prostaßlandins» ~, 363-368.
6.
Karim» S.M.M. & Hillier» K. (1975).Physiological roles and pharmacolo9ical ac%ions of prosZaglandins in relation to human reproduction. In P r o s t a g l a n ~ n s and ReproducZion, Ed. Karim, S.M.M., M.T.P., Lancaster, U.K., pp 23-75.
7.
Ligginss G.C., Fairclough, R.J., Grieves, S.A., Kendall, J.Z. & Knox, B.S. (1973).Mechanism of initiation of parturi%ion in the ewe. EecenZ Pro~ress in Hormone Research, 29, 111-150.
8.
Dawes, G.S. (1969) Foetal and Neonatal Physiolo~y. Year Book Medical, Chicago.
9.
Fencl, M. & Tulchinsky, D. (1975). Concentrations of cortisol in amnioZic fluid during pregnancy. New En@l. J. Med., 292, 133-136.
iO.
Challis~ J.E.G., Davies~ I.J., Benirschke, K., Hendrickx, A.G. & Ryan, K.J. (1975). The effecZs dexamethasone on the peripheral plasma concentrations of androstenedione, testosterone and cortisol in the pregnant rhesus monkey. Endocrinologys 96, 185-192.
ii.
Challis, J.R.G., Davies, I.J., & •yan, K.J. (1973). The concentraZion of progesterone, estrone and esZradiol-17~ in the plasma of pregnant rabbits. Endocrinolog~ , 93, 971-976.
12.
Hillier, K. & DilIey,S.R. (1974). Separation and radioimmunoassay of F prosZaglandins using silica gel micro columns. Prostag~andins , ~, 137-150.
13.
Challis, J.R.G., Calder, A.A., Dilley, S., Forster, C.S.~ Hillier, K., HunZer 3 D.J.S., MacKenzie, I.Z. & Thorburn G.D. ( 9 7 6 ) . Production of prostaglandin E and F by corpora luZea, corpora albicantes and sZroma fro~ Zhe human ovary. J. Endocr. 68 (in press).
14.
Hensby, C.N. (1974).Reduction of prosZaglandin E 2 to prostaglandin F_ by an enzyme in sheep blood° Biochim Biophys~~cta~ 348, 145-154.
15.
Comline, R.S. & Silver, M. (1972).The composition of foetal and maZernal blood during parturition in the ewe. J. Physiol (Lond.)272, 233-256.
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PROSTAGLANDINS
16.
Challis, J.R.G. & Thorburn,G.D. (1975).Prenatal endocrine function and the initiation of parturition. Br°Med. Bull., 31» 57-62.
17.
Boddy, K. & Dawes, G.S. Br.Med. Bull.~ 31, 3-7.
18.
Sun, F.F., & Armour, S.B. (1974).Prosta91andin 15hydroxy dehydrogenase and ~13 reductase levels in the lungs of maternal, fetal and neonatal rabbits. Prostaßlandins, Z, 327-338.
19.
Zuckerman, ~~ Reiss, U., & Rubinstein, I. (1974). Inhibition of human premature labor by indomethacin. Obstet. Gynecol., 44, 787-792.
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VOL. 11 NO. 6
(1975).Fetal breathing.
1049
PROSTAGLANDINS
7.3 pH 7.2 7.1 60 pCO2 [ ]
m
Z
40
~
J.
po2 E3 (mm Hg)
20 0 600
PGFtt
(pglml)
4O0 200
i tIt:l:lIiI[~
0 800
PGE
600
(pglml) 400 200
0 4O0
300 CORTISOL
(nglml)
200 IO0 0
40
30
2)
20
15
10
5
0 PP
DAYS BEFORE PARTURITION
F I G U R E i. T h e c o n c e n t r a ± i o n s ~ cortisol, PGE & PGF a n d the b l o o d gas a n d p H s t a t u s in c h r o n i c a l l y c a t h e t e r i z e d f e t a l l a m b s d u r i n g the last 35 days of p r e g n a n c y . C o r t i s o l & P G v a l u e s are the m e a n + $ . E . M . of 5 - 1 6 obs e r v a t i o n s on 5 f e t u s e s . B l o o d g a s e ß are the m e a n + S.E.M. o f 4 - 1 5 o b s e r v a t i o n s on the 4 of t h e s e f e t u s e s w h ~ c h h a d f e m o r a l a z t e r y c a t h e t e r s . T h e d a y of p a r t u r i t i o n has b e e n t a k e n as d a y 0. PP~ p o s t p a r % u m .
1050
JUNE 1976
VOL. 11 NO. 6
PROSTAGLANDINS
EWE 96 NORMAL PREGNANCY ~ 4
~
A
E
l=
PART'N
1600
~ . i,u Z
Z
800 Lu~~
~°°
g 0 (7226) ,t~ I I
1600 E
E
i
I
800
I
I I
~j...X
-
0300[-
'°o°of_ J
E >.~,
Ob
80
(85)
(88)
• o zm r=
~O
v
~»_o
40
0 124
128
132
136
140
144
148
OAYS OF PREGNANCY
F I G U R E 2. H o r m o n e c h a n g e s i n ovarian venous plasma in ewe pregnancy and parturition.
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VOL. 11 NO. 6
fetal and 96 during
uterolate
1051
PROSTAGLANDINS
EWE a 4 ==
79 NORMAL
PREGNANCY
108
112
116
120
DAYS
FIGURE 3. Hormone changes ovarian venous plasma in pregnancy and parturition.
1052
PART'N
1600
OF
124
128
132
136
140
PREGNANCY
in ewe
fetal and 79 during
uterolate
JUNE 1976
VOL. 11 NO. 6
