Stimulating effects of sorbitol and L-xylose on rat ileal Ca transport in vitro.
The direct effect of sorbitol and L-xylose on net intestinal calcium transport was compared to that of lactose, by determining unidirectional steady state calcium fluxes in segments of rat ileum in vitro under short-circuited conditions. The iso-molar addition of either 100 mM sorbitol, L-xylose, or lactose in mucosal buffer fluid increased the absorptive flux of Ca from mucosa to serosa to a similar extent and thus reversed ileal net Ca transport from net secretion to a zero net movement. The three substances decreased tissue conductance and reversed tissue polarity. At 200 mM, sorbitol induced a stimulation of net Ca transport due to an enhancement of absorptive Ca flux but in addition due to a decrease of secretory Ca flux from serosa to mucosa. The presence of 1 mM N-ethylmaleimide abolished the effects of sorbitol on ileal Ca flux. In conclusion, the present result shows that sorbitol, L-xylose, and lactose increase net Ca absorption to a comparable extent, in the absence of electrochemical or osmotic gradients. Such an absence of specificity suggests a stimulation of transcellular Ca transport related to the decrease of Na concentration in mucosal solution.
Lacour
B
B
INSERM U90, Hôpital Necker, Paris, France.
Ohan
J
J
Aznag
A
A
Drüeke
T B
TB
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004305:Dose-Response Relationship, Drug; D005033:Ethylmaleimide / Q000494:pharmacology; D007082:Ileum / Q000187:drug effects / Q000378:metabolism*; D007413:Intestinal Mucosa / Q000187:drug effects / Q000378:metabolism; D007785:Lactose / Q000494:pharmacology; D008297:Male; D008353:Mannitol / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013012:Sorbitol / Q000494:pharmacology*; D014994:Xylose / Q000494:pharmacology*
D008353:Mannitol; D013012:Sorbitol; D014994:Xylose; D007785:Lactose; D005033:Ethylmaleimide; D002118:Calcium