Effects of vasopressin on electrolyte transport across isolated colon from normal and dexamethasone-treated rats.
Vasopressin enhanced the absorption of Na+ and Cl- across the short-circuited colon descendens from normal rats. This effect of vasopressin results from an increase in the mucosal to serosal movement of Na+ and Cl- and a decrease in the serosal to mucosal movement of Cl- and was accompanied with a decrease in the short-circuit current (ISC). Neither the base-line absorption of Na+ and Cl-, the vasopressin-induced increase in Na+ and Cl- absorption nor the decrease in ISC were inhibited by amiloride in the colon from normal rats. Colon descendens from rats treated for 3 days with dexamethasone had remarkably higher transmural potential difference (p.d.), tissue conductance (Gt) and ISC. The absorption of Na+ across the short-circuited colon descendens from dexamethasone-treated rats was increased 3-fold when compared to colon from normal rats. The absorption of Cl- in normal rats was reversed to Cl- secretion in treated rats. Amiloride rapidly and reversibly decreased the p.d., Gt and ISC in colon from dexamethasone-treated rats. The transport of Na+ was nearly completely inhibited by amiloride in treated rats. In contrast to its enhancing effects on Na+ absorption in colon from normal rats vasopressin did not enhance Na+ absorption in colon from dexamethasone-treated rats. This enhancement of Cl- absorption by vasopressin was retained in colon from treated rats. This enhancement of Cl- transport was due solely to a decrease in the serosal to mucosal movement of Cl- and was accompanied with a decrease in ISC and Gt. The results support the hypothesis that vasopressin causes inhibition of the electrogenic secretion of Cl- in colon from dexamethasone-treated rats. Furthermore, the results suggest that the increase in the mucosal to serosal movement of Na+ and Cl- and the decrease in the serosal to mucosal movement of Cl- in colon from normal rats are caused by independent effects of vasopressin.
D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D002712:Chlorides / Q000378:metabolism*; D003106:Colon / Q000187:drug effects / Q000378:metabolism*; D003907:Dexamethasone / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007408:Intestinal Absorption / Q000187:drug effects; D008564:Membrane Potentials / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism*; D013997:Time Factors; D014667:Vasopressins / Q000494:pharmacology*
D002712:Chlorides; D014667:Vasopressins; D000584:Amiloride; D003907:Dexamethasone; D012964:Sodium