Differential Effects of Aldosterone and Vasopressin on Chloride Fluxes in Transimmortalized Mouse Cortical Collecting Duct Cells
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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 (I sc ). 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 × 10−7 m for 3 or 24 hr) stimulated I sc 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.
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