European Journal o f Pharmacology, 55 (1979) 345--346


© Elsevier/North-Holland Biomedical Press Rapid communication PGF2a STIMULATES RELEASE OF PGE2 and PGI2 IN THE ISOLATED PERFUSED RAT HEART * E.A.M. DE DECKERE, A.J. VERGROESEN and F. TEN HOOR Unilever Research Vlaardingen, The Netherlands

Received 22 March 1979, accepted 23 March 1979 Prostaglandin F2a has been described as a venoconstrictor and its intracoronary infusion has only a slight or no effect on myocardial blood flow. We found that PGF2a increased the coronary flow rate in the isolated rat heart. However, whereas PGE1, PGE2 and PGI2 increased the coronary flow rate immediately, the increase elicited by PGFm was delayed for about 1 min. We therefore investigated whether this delayed vasodilatory response might be explained by stimulation of the release of PGE2 and PGI2. Rat hearts were perfused with a Krebs-Henseleit buffer using the classical or a modified (De Deckere and Ten Hoor, 1977) Langendorff technique (perfusion pressure 9.3 kPa (70 mm Hg), stimulation frequency (360 min-l). In the modified technique, the caval veins axe tied off and the pulmonary artery is cannulated; 98% of the perfusate leaves the heart via the pulmonary artery and 2% drips from the apex. This latter fluid (Qi) is supposed to be interstitial effluent as it contains the main portion of the metabolites released by the heart (De Deckere and Ten Hoor, 1977). Solutions of PGF2a (0.7 or 1.4 pmol 1-1 ) in Krebs--Henseleit were infused into the perfusion fluid above the heart at a rate of 0.05 ml min -~, resulting in concentrations in the perfusion fluid of about 2.8 and 5.1 nmol 1-1. The coronary flow rates of the hearts were between 9.6 and 1 4 . 1 m l m i n -1 and * Please address correspondence to: E.T.J. Eikema, Editorial Department, Unilever Research, P.O. Box 114, 3130 AC Vlaardingen, The Netherlands.

PGF2a increased them by about 20%. The effect of PGF2a on the release of PGE2 and 6-oxo-PGF~a, the decomposition product of PGI2, was studied in Langendorff hearts. PGF2a (2.8 nmol l -t) was infused from t = 20 to t = 31 min. Perfusates of 5 hearts, before (control) and during PGF2~ infusion, were collected for 10 min and pooled. After addition of internal standards, the prostaglandins in the perfusates were extracted, purified by thin layer chromatography as their methoximated pentafluorobenzylesters and, after silylation, were measured by gas liquid chromatography (De Deckere et al., 1977). PGF2a increased the release of PGE2 and 6-oxo-PGF,a from 1.7 to 4.0 and from 7.7 to 16.0 pmol rain-' g-1 dry heart weight respectively. About the same effect was found with a PGF2a concentration of 5.0 nmol 1-I. The effect of PGF2a on the release of PGI2-1ike activity was studied in hearts perfused according to the modified Langendorff technique. PGF2a (5.1 nmol 1-1) was infused from t = 2 0 to t = 2 6 and from t = 34 to t = 40 min. Qi was collected on ice for periods of 5 min, after which the PGI2-1ike activity in Qi was determined by measuring the inhibitory activity of samples of Qi on ADP-induced rat platelet aggregation (De Deckere et al., 1977). PGF2, increased the release of PGI2like activity into Qi. When PGF2a was infused a second time, the increase was much smaller (table 1). Our results showed that PGF2a increased the release of PGE2 and PGI2. PGF2a may inhibit the decomposition of prostaglandins in

346 TABLE 1 Effect of PGF2a (5.1 nmol1-1) on the release of PGI 2like activity into Qi from isolated rat hearts perfused according to a modified Langendorff technique (n = 6; mean values -+ S.E.M.). Time I (min)

PGI2-1ike activity 2 (pmol PGE1 equivalents min-I g-1 dry weight)

Control PGF2~ Control


150 ± 27 3


102 + 18 3 ~ P

Control PGF2~

29--34 35--40

99 -+ 24 a 126-+ 27 4

The effect found may be of physiological i m p o r t a n c e . P G F 2 ~ is r e l e a s e d b y i s c h e m i c h e a r t m u s c l e o f m a n a n d d o g ( B e r g e r e t al., 1974). In dogs, PGFm attenuates the hemodynamic and biochemical responses to c o r o n a r y o c c l u s i o n ( G o l d f a r b e t al., 1 9 7 8 ) . These mitigating effects of PGF2~ might be explained by stimulation of the release of P G E 2 a n d PGI2.

< 0.01

Perfusion of the heart was started at t = 0. 2 PGI2-1ike activity was determined with respect to the inhibition by PGEI of the ADP-induced rat platelet aggregation. Heating of the Qi samples for 10 min at 37°C destroyed the inhibitory capacity. 3n=6. 4n=3.

the heart or be converted into PGE2 and PGI2. H o w e v e r , P G F 2 , c a n s t i m u l a t e t h e r e l e a s e o f a r a c h i d o n i c a c i d ( M u r o t a e t al., 1978). As PGF2~ also increases the contractile f o r c e in t h e i s o l a t e d r a t h e a r t , P G F 2 ~ m a y a c t as a c a l c i u m i o n o p h o r e a n d t h u s a c t i v a t e p h o s p h o l i p a s e A2.

References Berger, H.J., B. Zaret, L. Speroff, L. Cohen and S. Wolfson, 1974, Myocardial prostaglandin release during acute ischemia induced by atrial pacing in men and coronary occlusion in dogs, Circulation Suppl. 49--50, III, p. 122 (abstr.). De Deckere, E.A.M., D.H. Nugteren and F. Ten Hoot, 1977, Prostacyclin is the major prostaglandin released from the isolated perfused rabbit and rat heart, Nature 268, 160. De Deckere, E.A.M. and F. Ten Hoor, 1977, A modified Langendorfftechnique for metabolic investigations, Pfliigers Arch. 370, 103. Goldfarb, R.D., S.J. Mustafa and T.M. Glenn, 1978, Effects of prostaglandin F2(~ administration prior to coronary ligation, Amer. J. Physiol. 234, H718. Murota, S., T. Yokoi, L Morita and Y. Mori, 1978, Effect of various prostaglandins on the release of arachidonic acid from cultured fibroblasts, Biochem. Biophys. Res. Commun. 83,679.

PGF2 alpha stimulates release of PGE2 and PGI2 in the isolated perfused rat heart.

European Journal o f Pharmacology, 55 (1979) 345--346 345 © Elsevier/North-Holland Biomedical Press Rapid communication PGF2a STIMULATES RELEASE OF...
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