AJP - Lung Cellular and Molecular Physiology, Vol 259, Issue 4 230-L237, Copyright © 1990 by American Physiological Society
Aldosterone regulation of basolateral potassium channels in alveolar epithelium
B. Illek, H. Fischer and W. Clauss
Department of Veterinary Physiology, Free University of Berlin, Federal Republic of Germany.
To reveal the regulatory mechanism of the mineralocorticoid aldosterone on
basolateral K+ channels, the aldosterone-sensitive lung epithelium of
Xenopus laevis was investigated in Ussing chambers under voltage-clamp
conditions. Transepithelial measurements were supplemented by current
fluctuation analysis of short-circuit current noise in nonstimulated and
aldosterone-stimulated lung tissues. The addition of 10(-6) M aldosterone
stimulated short-circuit current from 11.3 +/- 2.0 to 27.8 +/- 4.8
microA/cm2 (n = 11) within 4-5 h. In the presence of an alveolar-to-pleural
K+ gradient, transepithelial K+ currents were induced by permeabilizing the
apical membrane with the pore-forming antibiotic amphotericin B. When the
local anesthetic lidocaine (25-1,000 microM) was added to the pleural
solution, macroscopic K+ current was dose dependently depressed. Lidocaine
induced a Lorentzian component in the power density spectra, and the corner
frequency increased linearly with blocker concentration. Aldosterone
treatment did not affect mean single K+ channel current, which was 1.5 +/-
0.12 pA corresponding to a 15-pS channel conductance, whereas the number of
basolateral K+ channels doubled. We conclude that the basolateral K+
channels in alveolar epithelia are a target site of aldosterone action.
