ADH-EVOKED [CL-](I)-DEPENDENT TRANSIENT IN WHOLE-CELL CURRENT OF DISTAL NEPHRON CELL-LINE A6

The effect of antidiuretic hormone (ADH) on a distal nephron cell line (A6) was studied using the whole cell patch-clamp technique. A6 cells were cultured on a permeable support filter for 10-14 days in media c ontaining 10% fetal bovine serum without supplemental aldosterone. In the unstimulated condition A6 cells had very small conductances of Na, K+, and Cl-. Arginine vasotocin (AVT, 140 mU/ml, 280 nM) evoked a '' transient'' increase in whole cell currents as did dibutyryl-adenosine 3',5'-cyclic monophosphate (5 mM). These transients consisted of two components; one was the nonselective cation conductance, and the other was the Cl- conductance. Activation of these conductances was depende nt on intracellular Cl- concentration ([Cl-](i)) At low [Cl-](i) (50 m M) both conductances were activated, whereas when [Cl-](i) was 80 mM, only the Cl- conductance was activated. At high [Cl-](i) (125 mM), bot h conductances were inhibited. It seems likely that the [Cl-](i) maint ained at a low level (less than or equal to 50 mM) is an important req uirement for A6 cells to respond to AVT.