ADH action on whole-cell currents by cytosolic Ca2+-dependent pathways in aldosterone-treated A6 cells

We studied the characteristics of the basal and antidiuretic hormone (arginine vasotocin, AVT)-activated whole cell currents of an aldosterone-treated distal nephron cell line (A6) at two different cytosolic Ca2+ concentrations ([Ca2+]c, 2 and 30 nm). A6 cells were cultured on a permeable support filter for 10 approximately 14 days in media with supplemental aldosterone (1 microM). At 30 nm [Ca2+]c, basal conductances mainly consisted of Cl- conductances, which were sensitive to 5-nitro-2-(3-phenyl-propylamino)-benzoate. Reduction of [Ca2+]c to 2 nm abolished the basal Cl- conductance. AVT evoked Cl- conductances at 2 as well as 30 nm [Ca2+]c. In addition to Cl- conductances, AVT induced benzamil-insensitive nonselective cation (NSC) conductances. This action on NSC conductances was observed at 30 nm [Ca2+]c but not at 2 nm [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.