AJP - Heart and Circulatory Physiology, Vol 247, Issue 2 237-H243, Copyright © 1984 by American Physiological Society
Sarcolemmal enzymes and Na+ -Ca2+ exchange in hypoxic, ischemic, and reperfused rat hearts
M. J. Daly, J. S. Elz and W. G. Nayler
Isolated spontaneously beating rat hearts were perfused in the Langendorff
mode and divided into four groups, i.e., control (aerobic), hypoxic (95%
N2-5% CO2), ischemic, and ischemic reperfused. After a total of 90 min of
perfusion, the sarcolemma was isolated and enzymatically characterized.
Ouabain-sensitive Na+-K+-ATPase was inhibited in all three experimental
groups, whereas K+-stimulated phosphatase activity was decreased only in
the ischemic and reperfused groups compared with control. 5'-Nucleotidase
activity was inhibited (P less than 0.05) only in the ischemic group.
Mg2+-ATPase activity was not different from control. Passive Ca2+ uptake
and Ca2+ efflux were not significantly altered by any of the interventions.
Na+-Ca2+ exchange rate, but not capacity, was decreased (by 32-42%) in the
ischemic group but this was partially reversed on reperfusion. These
results suggest that changes secondary to lack of flow rather than O2 play
a major role in the etiology of ischemic damage to the membrane and that a
15-min period of reperfusion after 60 min of ischemia does not exacerbate
this damage.
