Vasopressin-induced redistribution of binding sites for concanavalin A at the surface of epithelial cells from urinary bladder

Abstract

VASOPRESSIN promotes water movement across the epithelium of the distal portion of mammalian renal tubule and amphibian urinary bladder^1,2. The hormone also elicits a general, non-selective increase in the transcellular permeation of lipophilic solutes³ and a decrease in the discrimination between straight- and branched-chain isomers^4,5. Such changes in the permeability of amphibian urinary bladder are limited to the apical membrane of those epithelial cells rich in intracellular secretion granules^6,7. These granules, some of which may correspond to lysosomes⁸, are observed to migrate to the mucosal membrane of toad bladders treated with oxytocin or cyclic AMP⁹. Moreover, treatment with vasopressin provokes the extracellular release of acid hydrolases at the apical surface of cells from bullfrog bladder¹⁰. Additional evidence shows that repression of such hydrolase activity at the external surface reduces the hormone-induced water flow observed across the intact epithelium⁷. My present investigation extends these observations by providing direct evidence in epithelial cells from bullfrog bladder for vasopressin-induced rearrangement into clusters of binding sites for concanavalin A (con A) which are otherwise randomly disposed at the surface of control cells. This hormone effect is inhibited by prior incubation of cells with the microtubule-disrupting drug, colchicine. In addition, colchicine treatment antagonises the enhancement of extracellular hydrolase release and transepithelial water flow attributable to vasopressin action.