INHIBITORY EFFECT OF SODIUM URSODEOXYCHOLATE ON BASAL AND STIMULATED SHORT-CIRCUIT CURRENT ACROSS THE ISOLATED TOAD SKIN

The effect of sodium ursodeoxycholate (U) on short-circuit current (SC C), an index of basal and stimulated net ion transport across isolated skins of Bufo arenarum toads, was tested, U inhibited basal SCC when added to the epidermal side of the skins, The inhibitory effect was re versible after rinsing the preparation during 60 min, U also inhibited the natriferic response to oxytocin, db-cAMP and theophylline by 82%, 49% and 47%, respectively, Inhibition of SCC by exposure to U was rev ersed by the polyene antibiotic nystatin, In turn, SCC induced by nyst atin in the amiloride-treated skin was insensitive to U and blocked by ouabain, a Na+, K+-ATPase inhibitor. These results strongly suggest t hat the effect of U is exerted at the apical membrane of sodium transp orting cells, and rule out the existence of an additional site of inhi bitory action of U.