Evidence for apical sodium channels in frog lung epithelial cells

摘要: To reveal the mechanism of Na+ transport across Xenopus lung epithelium, we recorded short-circuit current (Isc), transepithelial resistance (Rt), and noise spectra while isolated tissues were mounted in an Ussing-type chamber. Mean values Isc Rt obtained tissue was bilaterally incubated with NaCl-Ringer solution = 11.57 +/- 1.19 microA.cm-2 0.82 0.07 k omega.cm2. Amiloride added to mucosal (apical) side depressed by 61 99%. Ouabain abolished totally when basolateral compartment. Adenosine 3',5'-cyclic monophosphate (cAMP), epinephrine, a variety other compounds did not alter significantly. Transepithelial depolarization serosal KCl reduced 6.22 1.37 microA.cm-2. Amiloride-sensitive kinetics amiloride interaction significantly affected depolarization. Fluctuation analysis presence revealed Lorentzian component power density spectrum indicating apical channels. Assuming pseudo-first order kinetics, calculated single channel currents (iNa) (M): iNa 0.29 0.04 pA M 0.24 micron 2. Our results show that route for through epithelial cells follows classical Koefoed-Johnson-Ussing model tight epithelia.