Slow activation of chloride currents during hypotonicity in rabbit proximal convoluted tubule (PCT) cells in culture.

Using a patch-clamp technique the hypotonic-induced potassium (K) and chloride (Cl) currents were studied in cultured kidney proximal convoluted tubule (PCT) cells. When a PCT cell was exposed to a low-osmotic solution, cell membrane potential (Vm) initially hyperpolarized and then depolarized toward an original level (a pipette-filling solution was 140 mM KCl with 0 Ca plus 0.08 mM EGTA). When Cl was replaced by gluconate in the pipette, a secondary depolarization was not observed. Time courses of the maximum level of the K and Cl currents were 50 and 240s, respectively. These results suggest that K and Cl currents were activated by hypotonic cell-swelling and that the Cl currents were activated in a slower time course than K currents.