AJP - Gastrointestinal and Liver Physiology, Vol 258, Issue 1 45-G51, Copyright © 1990 by American Physiological Society
Mechanisms of changes in K+ balance on reduction and reestablishment of flow in isolated rat liver
L. Sestoft and M. Folke
Department of Medicine F, Gentofte Hospital, Hellerup, Denmark.
The effects of low flow and reestablished normal flow on K+ balance and
carboxylic acid balance was studied in perfused liver of 48-h starved rats
at perfusate pH 7.4 and 6.8. The rate of net K+ release induced by ouabain
was 1.8 mumol.min-1.g-1 at pH 7.4 and 1.4 mumol.min-1.g-1 at pH 6.8.
Lowering of flow to 30% normal was accompanied by a transient, diphasic
loss of K+ (max 0.15 mumol.min-1.g-1). Reestablished normal flow was
immediately accompanied by a monophasic K+ uptake (max 0.35
mumol.min-1.g-1). These changes in potassium balance were independent of
perfusate pH. Reduction of flow caused an almost immediate depolarization
of 4 mV followed by a steady tendency to repolarization. Reestablished
normal flow induced a transient hyperpolarization. Production of carboxylic
acids during the low flow period did not correlate with the diphasic time
course of K+ loss, and carboxylic acid uptake after reestablishment of flow
did not correlate with the transient uptake of K+. The data show that the
initial phase of K+ loss during low flow is due to inhibition of the
Na(+)-K(+)-pump; the second phase may be reasonably explained by increased
K+ permeability concomitant to cellular volume regulation.
