AJP - Regulatory, Integrative and Comparative Physiology, Vol 259, Issue 5 936-R942, Copyright © 1990 by American Physiological Society
Net basolateral potassium flux and short-circuit current in ouabain-treated frog skin
T. C. Cox and R. E. Woods
Department of Physiology, Southern Illinois University School of Medicine, Carbondale 62901.
A new technique has been developed to correlate K loss from cells (JK)
across the basolateral membrane into a K-free ouabain Ringer solution and
short-circuit current (Isc) for a model Na-transporting epithelium, the
frog skin. Distinct differences were observed when the tissue was bathed in
sulfate or chloride Ringer. In sulfate Ringer, K-free ouabain treatment
caused both JK and Isc to decline in a nearly parallel fashion with time.
JK-Isc was approximately 1 microA/cm2. In sulfate Ringer, isoproterenol
caused parallel increases, whereas amiloride (apical side) caused parallel
decreases in JK and Isc. In chloride Ringer, K-free ouabain treatment
caused Isc to decline at a slightly faster rate than JK.JK-Isc was
approximately 8 microA/cm2. Bumetanide decreased JK with very little effect
on Isc. Barium caused small parallel changes in both Isc and JK. Amiloride
decreased Isc with very little effect on JK. These experiments show that
after ouabain treatment changes in JK from the cells across the basolateral
membrane can largely account for changes in Isc. However, JK also occurs
via neutral mechanisms and perhaps from cells not related to the transport
pathway, demonstrating that there is not always a tight coupling of K loss
at the basolateral membrane with Na entry across the apical membrane.
