Early effects of aldosterone on the basolateral potassium conductance of A6 cells

Aldosterone increases the basolateral conductance in target epithelia. The basolateral membrane of tight epithelia contains two different types of K+ conductances (GK), a "resting" and a volume-activated GK. We have studied the early effects (at 4 hours) of 500 nmol/l aldosterone on the basolateral membrane GK of A6 cells (a Xenopus laevis kidney cell line), after the permeabilization of the apical membrane with amphotericin B. In the presence of a 97 to 3 mmol/l apical to basolateral K+ gradient, the "resting", inward rectifying GK was similar in control and aldosterone treated cells. In contrast, aldosterone induced a 2-fold increase of the volume-activated quinidine sensitive GK.