AJP - Renal Physiology, Vol 245, Issue 3 312-F321, Copyright © 1983 by American Physiological Society
Effects of ouabain and furosemide on basolateral membrane Na efflux of frog skin
T. C. Cox and S. I. Helman
The kinetics of Na tracer fluxes were reinvestigated in isolated epithelia
of frog skin in which the unstirred layers of the corium were removed. The
rate of appearance of 22Na in the basolateral solution (JNa13) conformed to
a single exponential for tracer buildup with a mean t1/2 of 1.9 min. The Na
transport pool labeled isotopically from the apical solution was about 40
neq/cm2 for epithelia bathed in either a chloride or sulfate Ringer
solution. Basolateral-to-apical solution unidirectional Na flux (JNa31) was
low, averaging 0.7 microA/cm2 and remained low for 40 min of ouabain
treatment of the epithelia. In agreement with electrophysiological data,
ouabain at 10(-4) M caused an acute inhibition (less than 1 min) of the Na
efflux at the basolateral membrane (JNa23), falling to 40.6 and 26.7% of
control for epithelia bathed in Cl and SO4 Ringer, respectively. Although
furosemide exerted little or no consistent effect on the Na flux of control
epithelia, this drug in ouabain-poisoned epithelia caused a substantial
inhibition of a neutral, chloride-dependent, ouabain-insensitive Na efflux.
It is suggested that ouabain "induces" a neutral mechanism of Na transport
at the basolateral membrane of the cells that is chloride dependent and
furosemide sensitive.
