Cl transport across the basolateral membrane of principal cells in frog skin.

Measurements of cellular electrolyte concentrations were performed using electron microprobe analysis to further characterize the Cl transport across the basolateral membranes of principal cells. Cellular Cl loss into a Cl-free serosal solution can be prevented by combined application of the Cl channel blocker diphenylamine-2-carboxylate and the cotransport inhibitor bumetanide, indicating a cellular Cl exit across a cotransport system. Recovery of the cellular Cl concentration after Cl depletion requires the simultaneous serosal presence of Na, K and Cl. Cellular Rb uptake measurements indicate that Rb instead of K is accepted by the cotransporter. Whereas after Cl depletion more Rb than Cl is taken up into the cells by the cotransporter, almost no Rb enters the cells via this transporter under control conditions. The data suggest that the high cellular Cl concentration is maintained by a Na-K-2Cl cotransporter which during cellular Cl reuptake seems to work like a shuttle but is almost completely silent under control conditions.