Bio~hlmtca et Bloph~sl¢a A~ta, 419 (1976) ~14-~;19

C' Elsevler Scientific Pubhshmg Company, Amsterdam - Printed m The NLtherlands BBA 77173 SODIUM

I O N T R A N S P O R T IN

ISOLATED INTESTINAL

EPITHELIAL

CELLS lI

COMPARISON

OF

THE

EFFECT

OF

ACTIVELY

TRANSPORTED

S U G A R S ON S O D I U M ION E F F L U X I N CELLS I S O L A T E D F R O M J E J U N U M AND ILEUM

D GRANT GALL* and DIANNE CHAPMAN Department o/ Pedtatrlcs, UntLerslty o/ Toronto and the Research Instttute, Tile Hospital [or Sl~L Children, 555 Umt,erstt~ Atenue, Toronto, Ontario, ~5G 1)(8 (Canada)

IRecel~ed June 30th, 1975)

SUMMARY Na + transport studies m intestinal epahel~al cells m&cate that enterocytes from different regions of the small zntestme &ffer m their response to actively transported sugars 1 Compared w~th sugar-free medmm total Na + efflux rate constants from Isolated rat jejunal cells were significantly increased when medium contained actively transported sugars, glucose and galactose, but not when medium contained fructose 2 In contrast total Na + efflux rate constants from isolated rat ileal cells did not respond to actively transported sugars, glucose and galactose 3 Similar results for the effect of actively transported sugars on Na t efflux were obtained for isolated rabbit jejunal and ileal epithelial cells 4 Passive Na + efflux rate constants for isolated jejunal and ileal enterocytes are not s~gnlficantly &fferent, indicating similar permeablhty characteristics

INTRODUCTION Although the ileum possesses several specmhzed functions including bile salt [1] and B-12 absorption [2], the effect of actively transported sugars and amino acids on Na + movement is thought by most to be similar in je.lunum and ileum [3, 4] However, several authors have reported significant differences between,lejunum and ileum concerning the interaction of actively transported non-electrolytes and Na + transport Barry et al [5] reported that water absorptaon, which as thought to be passive and secondary to active solute transport [4], m the jejunum was glucose dependent, whereas, in the ileum the ma,lonty of total water absorption was glucose independent Fordtran et al [6] m in vlvo perfuslon stu&es of human intestine found * To whom correspondence should be sent

315

that Na + absorption m the jejunum was sttmulated by glucose and galactose but not m the deum The experiments m the present paper, which deals with the effect of actively transported sugars on Na + transport from isolated jejunal and ileal eplthehal cells, demonstrates slgntficant differences between jejunal and ileal cells MATERIALS AND METHODS

Animals used were male Wlstar rats weighing 150-300 g and New Zealand white rabbits weighing 1 5-4 0 kg Epithelial cells were isolated from a 30-cm segment ofjelunum starting 10 cm distal to the ligament of Treltz and from a 30-cm segment of Ileum, m rats immediately proximal to the lleocecal valve, m rabbits proximal to the end of the mesenteric attachment of the appendix, by mechanical vlbrat~on as previously described [7] Enterocytes isolated by this technique are mature cells from the vllh and not crypt cells [7] The composition of the solutions and the technique used for measuring Na + etttux from isolated small intestinal epithelial cells were identical to that previously described except the ~solatlon solution and MgCI2 wash solution contained 5 m M Trls/Trls HC1 buffer instead of 2 m M Trls buffer [7] Briefly, harvested epithelial cells were loaded with radloactwe Na + by suspending them in incubation medium containing 22Na+, then washed w a h MgC12 wash solution and returned to trace-free medium Na + efflux was ascertained by measuring the rate of appearance of radioactive N a + in the medium The rate constants are reported as the amount of Na + exchange per h The efflux constant remaining after lnh~bmon with 1 m M ouabam is defined as passive efflux Sugars, ouabaln and phlondzln, when used were present in the incubation medium during both loading and efflux periods RESULTS

Effect of acttvely transported sugars Table I compares total and passive N a + efflux rate constants obtained in the presence of actively transported sugars with those obtained in sugar-free medium for jejunal and ileal epithelial cells from rats We confirmed our previous findings that actively transported sugars, glucose and galactose at a 10 m M concentration, significantly stimulated the total N a + efflux rate constant from isolated jejunal eplthehal cells [7] In contrast total Na + efflux rate constants obtained in the presence of these same sugars at identical concentration for isolated ileal epithelial cells were not significantly different from that found for sugarfree medium The total rate constant for jejunal cells In sugar-free medium was significantly less than that found for ileal cells in sugar-free medium and in medium contaming glucose or galactose (P < 0 0005) Passive efflux rate constants for jejunal and deal cells m the presence of actively transported sugars were not significantly different from that found in sugar-free medium Passive rate constants in sugar-free medium for ileal and jejunal cells were also not significantly different Effect of fructose Table I includes results for the effect of fructose on N a + efflux from isolated rat jejunal eplthehal cells Fructose is not actively transported by the Na+-dependent glucose-galactose carrier mechanism [8] but can be utilized by rat jejunal tissue as an energy source for ion transport [9] In isolated jejunal cells the total N a + efflux rate constant m the presence of fructose was not significantly d~fferent

z;16 TABLE 1 EFFECT OF MONOSACCHAR]DES AND ILEAL EPITHELIAL CELLS

ONNa + EFFLUX

Jelunum

P

**

FROM 1SOLAqEI)

Ileum

P

RAT JEJLNAt

**

Total N a + effiux rate c o n s t a n t (h ~)* Sugar-flee m e d i u m 10 m M m a n m t o l

9 6 + 0 2 (100)

146t06(51)

M o n o s a c c h a H d e s actively t r a n s p o r t e d 10 m M glucose 14 0 + 0 4 (84) 10 m M galactose 11 5 ~ 0 4 (42)

0 0005 00005

M o n o s a c c h a n d e n o t actwely transported 10 m M fructose 10 ?, ~0 3 (38)

ns

14 3 ~0 5 (44) 135+07(?,5)

n ns

Passtve (1 m M o u a b a m ) N a + efflux rate t.onstant [ h - t ) * Sugar-free m e d m m 10 m M m a n m t o l

6 7 - - 0 2 [52)

7 I 4 0 5 (26)

M o n o s a c c h a r l d e s actively t r a n s p o r t e d 10 m M glucose 6 9= 0 3 (47) I0 m M galactose 7 0 ~0 3 (23)

ns n s

M o n o s a c c h a n d e n o t actl~el~ transported 10 m M fructose 7 1 J 0 ?, (37)

l) S

8 0 0 3 (39) 6 5 - 0 5 (23)

ns 13 s

* E a c h value represents m e a n - - S E with the n u m b e r o f o b s e r ~ a t t o n s m parentheses ** C o m p a r e d with sugar-free m e d m m n s , n o t slgmficant T A B L E 11 EFFECT OF05 mM PHLORIDZIN ON Na + EFFLUX FROM ISOLATED CELLS INTH[: A B S E N C E O F A N D IN T H E P R E S E N C E O F l0 m M G A L A C T O S E Total N a + efflu,~ rate c o n s t a n t [h -~ ) E a c h value represents the m e a n + S E ~Jth the n u m b e r o f observations m parentheses Jejunum

Ileum

Phlondzm (0mM) Manmtol 10raM Galactose 10raM

90--03[2?,) II 3 J 0 4 ( 2 4 )

PhlorJdzm (05raM)

P

Phlondzm [0mM)

PhloNdzm ( 0 5 raM)

P

90±04(2?,)

ns

17,8£05(78)

136 ~08(22)

n~

89=-0?,(26)

00005

127+08[17)

129 t I 2 ( 1 5 )

n~

medmm,

was stgmficantly

n s , n o t slgmficant from

that

m sugar-free

but

less than

that

obtained

m

medmm containing glucose (P < 0 0005) or galactose (P < 0 025) The passwe efflux rate constant m the presence of fructose was not slgmficantly d~fferent from that m sugar-free

medmm

or m rnedmm

containing

glucose or galactose

317

Effect ofphlorMzm Table II c o m p a i e s the effect o f p h l o r l d z l n on N a + efltux f r o m r a t ileal epithelial cells to o u r previous findings for j e j u n a l cells [7] I n c o n t r a s t to j e j u n a l cells, in which galactose stimulates the t o t a l efftux rate c o n s t a n t a n d this increase is completely a b o l i s h e d by phlorIdzln, the presence o f galactose does n o t p r o d u c e an increase in the t o t a l rate c o n s t a n t f r o m ileal cells a n d p h l o r l d z l n has n o i n h i b i t o r y effect TABLE II1 EFFECT OF MONOSACCHARIDES ON Na + EFFLUX FROM ISOLATED RABBIT JEJUNAL AND ILEAL EPITHELIAL CELLS Jejunum

P

Sodium ion transport in isolated intestinal epithelial cells. II. Comparison of the effect of actively transported sugars on sodium ion efflux in cells isolated from jejunum and ileum.

Na+ transport studies in intestinal epithelial cells indicate that enterocytes from different regions of the small intestine differ in their response ...
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