Aldosterone regulation of basolateral potassium channels in alveolar epithelium.
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.
Illek
B
B
Department of Veterinary Physiology, Free University of Berlin, Federal Republic of Germany.
Fischer
H
H
Clauss
W
W
D000450:Aldosterone / Q000494:pharmacology*; D000818:Animals; D004553:Electric Conductivity; D004594:Electrophysiology / Q000379:methods; D004848:Epithelium / Q000187:drug effects / Q000502:physiology; D066298:In Vitro Techniques; D007700:Kinetics; D008012:Lidocaine / Q000494:pharmacology; D008954:Models, Biological; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology*; D011650:Pulmonary Alveoli / Q000502:physiology*; D014982:Xenopus laevis
D015221:Potassium Channels; D000450:Aldosterone; D008012:Lidocaine