Actin-based cytoskeleton regulates a chloride channel and cell volume in a renal cortical collecting duct cell line

The regulatory volume decrease (RVD) of a renal cortical collecting duct cell line (RCCT-28A) exposed to a hypotonic solution was studied using electronic cell sizing to measure cell volume and the patch clamp technique to measure Cl- channel activity. Results demonstrate that RVD was mediated in part by KCl loss through separate K+ and Cl- channels. The Cl- channel had a conductance of 305 pS and was activated by cell swelling, membrane stretch, and disruption of F-actin by dihydrocytochalasins. In contrast, stabilizing F-actin with phalloidin prevented swelling and stretch activation of the Cl- channel and inhibited the RVD. Thus, the state of actin polymerization regulates the probability of the 305 pS Cl- channel being open. Short actin filaments activate whereas long actin filaments inactivate the channel. Taken together, our studies suggest that RVD in this renal collecting duct cell line cell is mediated in part by a 305 pS Cl- channel, which is activated, during cell swelling, by a signaling pathway that includes disruption of F-actin.