EFFECTS OF VASOPRESSIN ON ELECTROLYTE TRANSPORT IN LIZARD INTESTINE

Vasopressin applied serosally had no effect on electrical parameters and unidirectional Na and Cl fluxes across an in vitro short circuited preparation of lizard ileum. Short circuit current (Isc) and transmural potential difference (PD) across colon were decreased by vasopressin and increased by cyclic AMP. Vasopressin increased the mucosal-to-serosal flux of sodium and chloride across short circuited colon. Cyclic AMP had no effect on the rate of Na absorption but reversed Cl absorption to secretion. Vasopressin enhanced the net absorption of water across the colon but had no effect on absorption across ileum. Cyclic AMP activity in homogenates of colon was not altered by vasopressin but was increased by theophylline. It is concluded that the colonic response of the lizard colon to vasopressin is mediated by a noncyclic AMP mechanism. © 1990 Springer-Verlag.