Cell swelling activates the K+ conductance and inhibits the Cl- conductance of the basolateral membrane of cells from a leaky epithelium

Abstract

Necturus gallbladder epithelial cells bathed in 10 mM HCO3/1% CO2 display sizable basolateral membrane conductances for Cl- (G(Cl)/b) and K+ (G(K)/b). Lowering the osmolality of the apical bathing solution hyperpolarized both apical and basolateral membranes and increased the K+/Cl- selectivity of the basolateral membrane. Hyperosmotic solutions had the opposite effects. Intracellular free-calcium concentration ([Ca2+](i)) increased transiently during hyposmotic swelling (peak at ~30 s, return to baseline within ~90 s), but chelation of cell Ca2+ did not prevent the membrane hyperpolarization elicited by the hyposmotic solution. Cable analysis experiments showed that the electrical resistance of the basolateral membrane decreased during hyposmotic swelling and increased during hyperosmotic shrinkage, whereas the apical membrane resistance was unchanged in hyposmotic solution and decreased in hyperosmotic solution. We assessed changes in cell volume in the epithelium by measuring change