Membrane-metabolic coupling and ion homeostasis in anoxia-tolerant
and anoxia-intolerant hepatocytes.
Krumschnabel, Gerhard, Christina Biasi, Pablo J. Schwarzbaum, and
Wolfgang Wieser.
Institut f[umlaut]ur Zoologie, Abteilung f[umlaut]ur
[diaeresis]okophysiologie, Universit[umlaut]at Innsbruck,
Technikerstra[beta]e 25, A-6020 Innsbruck, Austria, Instituto de
Qu[acute]imica y Fisicoqu[acute]imica Biol[acute]ogicas (Facultad de
Farmacia y Bioqu[acute]imica), Universidad de Buenos Aires, Junin
956, 1113 Buenos Aires, Argentina
APStracts 2:0321R, 1995.
The relationship between membrane function and energy metabolism was
studied in rainbow trout hepatocytes, an anoxia intolerant cell
system, and compared to the situation in hepatocytes from the
goldfish, a typical anoxia tolerant species. In trout hepatocytes,
both under normoxia and under chemical anoxia, inhibition of ATP
consumption by the Na+pump induced a decrease of ATP production of
the same magnitude. In response to chemical anoxia total ATP
production was reduced to 15%, Na+pump activity to 22% of the control
rate under normoxia. Measurement of the cellular ATP content under
these conditions revealed that despite the reduction of Na+pump
activity the cells became rapidly depleted of ATP, the time course of
this process resembling that observed in the anoxic rat hepatocyte.
This is in contrast to the responses of goldfish hepatocytes, where
during chemical anoxia 1) inhibition of the Na+pump did not lead to a
corresponding reduction of ATP production, and 2) ATP levels, after a
transient decrease, stabilized at a new steady state. In order to
investigate the consequences of chemical anoxia on ion homeostasis,
efflux and uptake rates of K+ were determined simultaneously. In the
trout cells chemical anoxia led to a decoupling of influx and efflux
rates, the latter exceeding the former 3- to 8-fold. In contrast,
goldfish hepatocytes were able to preserve ion homeostasis by a
concerted decrease of Rb+uptake and K+efflux, so that the net flux of
K+ was always close to zero. In neither species did chemical anoxia
induce any change in pump density. Other potential control mechanisms
are briefly discussed.
Received 1 March 1995; accepted in final form 18 October 1995.
APS Manuscript Number R142-5.
Article publication pending Am. J. Physiol. (Regulatory Integrative
Comp. Physiology).
ISSN 1080-4757 Copyright 1995 The American Physiological Society.
Published in APStracts on 8 December 95