AJP - Heart and Circulatory Physiology, Vol 246, Issue 6 858-H864, Copyright © 1984 by American Physiological Society
Regulation of pyruvate dehydrogenase complex in ischemic rat heart
T. B. Patel and M. S. Olson
The effect of flow-induced ischemia on the rate of pyruvate decarboxylation
and the activation state of the pyruvate dehydrogenase multienzyme complex
was investigated in the isolated, perfused rat heart. Pyruvate
dehydrogenase activity in the heart decreased significantly during
flow-induced ischemia and was a function of changes in the activation state
(i.e., active/total activity) of the enzyme complex. In the absence of
pyruvate, the activation state of pyruvate dehydrogenase decreased from
nearly 100% active at the normal flow rate (10 ml/min) to 20% active as the
flow was reduced to 0.5 ml/min. At high pyruvate levels (5 mM), the
activation state increased from nearly 70% active at control flow rates to
100% active during ischemia. At an intermediate pyruvate concentration (0.5
mM), the enzyme complex was maintained at a relatively low activation state
(30-35% active) throughout the range of flow rates tested. Ischemia caused
elevated perfusate lactate concentrations only when the flow rates were
less than 5.0 ml/min. The activation state of the pyruvate dehydrogenase
complex in hearts perfused with glucose was also decreased during ischemia.
