The effects of aldosterone and vasopressin on Cl- transport were investigated in a mouse cortical collecting duct (mpkCCD) cell line derived from a transgenic mouse carrying the SV40 large T antigen driven by the proximal regulatory sequences of the L-pyruvate kinase gene. The cells had features of a tight epithelium and expressed the amiloride-sensitive sodium channel and the cystic fibrosis transmembrane conductance regulator (CFTR) genes. dD-arginine vasopressin (dDAVP) caused a rapid, dose-dependent, increase in short-circuit current (Isc). Experiments with ion channel blockers and apical ion substitution showed that the current represented amiloride-sensitive Na+ and 5-nitro-2-(3-phenylpropylamino)benzoate-sensitive and glibenclamide-sensitive Cl- fluxes. Aldosterone (5 x 10(-7)M for 3 or 24 hr) stimulated Isc and apical-to-basal 22Na+ flux by 3-fold. 36Cl- flux studies showed that dDAVP and aldosterone stimulated net Cl- reabsorption and that dDAVP potentiated the action of aldosterone on Cl- transport. Whereas aldosterone affected only the apical-to-basal 36Cl- flux, dDAVP mainly increased the apical-to-basal Cl- flux and the basal-to-apical flux of Cl- to a lesser extent. These results suggest that the discrete dDAVP-elicited Cl- secretion involves the CFTR and that dDAVP and aldosterone may affect in different ways the observed increased Cl- reabsorption in this model of mouse cultured cortical collecting duct cells.