AJP - Regulatory, Integrative and Comparative Physiology, Vol 250, Issue 4 573-R579, Copyright © 1986 by American Physiological Society
Reoxygenation injury in isolated hepatocytes: effect of extracellular ATP on cation homeostasis
H. Hayashi, I. H. Chaudry, M. G. Clemens, M. J. Hull and A. E. Baue
The aims of this study were to determine 1) the effects of anoxia and
reoxygenation on electrolytes and ATP content of isolated hepatocytes and
2) whether exogenous ATP-MgCl2 has any beneficial effects on the cellular
alterations that are produced during the reoxygenation period. After 90 min
anoxia, intracellular Na and inorganic phosphate (Pi) increased, K and ATP
decreased, whereas Ca and Mg did not change. After 60 min of reoxygenation,
intracellular Mg and Na levels decreased, Ca increased, and Pi levels
returned to normal, but ATP levels remained low. These results suggest that
the plasma membrane is relatively impermeable to divalent ions such as
Ca2+, Mg2+, and HPO2-4 during anoxia but becomes permeable to them after
reoxygenation. When anoxic cells were treated with ATP-MgCl2 during
reoxygenation, intracellular ATP and Mg levels increased, but accumulation
of Ca and Pi was also observed. Thus enhancement of Mg transport and
specific stimulation of Ca-Pi sequestration occurs with ATP-MgCl2
treatment. Na and K levels exhibited biphasic reciprocal dose-response
changes to ATP-MgCl2 treatment; i.e., 0.1 mM ATP-MgCl2 (low-dose) treatment
increased K and decreased Na, whereas 1 mM ATP-MgCl2 (high-dose) treatment
decreased K and increased Na. These results indicate that although addition
of a single high-dose ATP-MgCl2 was deleterious over a period of 60 min,
low-dose ATP-MgCl2 accelerates the recovery of postanoxic cellular
electrolyte homeostasis.
