ADH ACTION ON WHOLE-CELL CURRENTS BY CYTOSOLIC CA2-DEPENDENT PATHWAYSIN ALDOSTERONE-TREATED A6 CELLS()

We studied the characteristics of the basal and antidiuretic hormone ( arginine vasotocin, AVT)-activated whole cell currents of an aldostero ne-treated distal nephron cell line (A6) at two different cytosolic Ca 2+ concentrations ([Ca2+](c), 2 and 30 mM). A6 cells were cultured on a permeable support filter for 10 similar to 14 days in media with sup plemental aldosterone (1 mu M). At 30 nM [Ca2+](c), basal conductances mainly consisted of Cl- conductances, which were sensitive to 5-nitro -2-(3-phenylpropylamino)-benzoate. Reduction of [Ca2+](c) to 2 nM abol ished the basal Cl- conductance. AVT evoked Cl- conductances at 2 as w ell as 30 nM [Ca2+](c). In addition to Cl- conductances, AVT induced b enzamil-insensitive nonselective cation (NSC) conductances. This actio n on NSC conductances was observed at 30 nM [Ca2+](c) but not at 2 nhl [Ca2+](c). Thus, cytosolic Ca2+ regulates NSC and Cl- conductances in a distal nephron cell line (A6) in response to AVT. Keeping [Ca2+](c) at an adequate level seems likely to be an important requirement for AVT regulation of ion conductances in aldosterone-treated A6 cells.