Cyclic GMP-activated channel activity in renal epithelial cells (A6)

We studied the effects of guanosine 3',5'-cyclic monophosphate (cGMP) and nitroprusside on ion channels in the apical membrane of confluent A6 cells (a distal nephron cell line) cultured on permeable supports for 10-14 days using patch clamp techniques. In cell-attached patches without any detectable channel activity, activity of a non-selective cation channel with a single-channel conductance of 1 pS was observed after adding nitroprusside. After adding cGMP to the cytosolic surface of inside-out patches with no detectable channel activity, we observed single channel activity similar to the channel observed after adding nitroprusside. These observations imply that nitroprusside activates a non-selective cation channel with small single channel conductance (1 pS) via an increase in cGMP which activates the channel.