AJP - Renal Physiology, Vol 249, Issue 2 185-F191, Copyright © 1985 by American Physiological Society
Electrogenicity of the Na-K-ATPase pump in bullfrog cornea epithelium
G. Carrasquer, S. Ahn, M. Schwartz and W. S. Rehm
The effect of changing the K concentration in the aqueous solution was
studied in the frog cornea. In general, when the K concentration was
increased from 4 to 20 or 79 mM, the transepithelial PD and resistance
decreased. If K was decreased from 79 to 4, 20 to 4, or 4 to 0 mM, or any
other combination, the PD and resistance increased. These are normal PD
responses. If after a K-free period of more than 5-10 min the K was
increased to 4 mM, the PD increased, an anomalous PD response. If K was
increased from 0 to 20 mM, there was an initial PD increase (anomalous
response) followed by a PD decrease (normal response). If K was increased
from 0 to 79 mM the PD decreased, normal response only. The resistance
decreased with every increase in K concentration. Anomalous responses were
abolished in Na-free solutions and in the presence of both 10(-3) M ouabain
and 10(-4) M vanadate in the aqueous solution. We interpret the results on
the basis of two pathways, a simple K-conductive pathway and an
electrogenic Na-K-ATPase pump pathway with more Na's than K's per cycle.
The normal or anomalous PD responses to changes in aqueous K concentration
depend on the relative resistance of the two pathways.
