The time course of changes in the myocardial levels of
nonesterified fatty acids (
NEFA),
adenosine triphosphate (
ATP),
creatine phosphate (CrP) and
lactate, and those in the cardiac mechanical function during
ischemia and reperfusion was investigated in the isolated, perfused, working rat heart.
Ischemia was produced by lowering the afterload pressure from 60 to 0 mm Hg, and reperfusion resulted from raising the afterload pressure to 60 mm Hg.
Ischemia stopped the heart beat, and increased the myocardial levels of unsaturated
NEFA (such as arachidonic, palmitoleic, and
linoleic acids) as a function of the ischemic period; it decreased the myocardial levels of
ATP and CrP, and increased the myocardial level of
lactate. The level of
arachidonic acid increased when the myocardial level of
ATP fell below 5 mumol/g dry weight. Reperfusion after
ischemia started the heart beat, and restored the mechanical function which depended on the preceding ischemic period. Reperfusion also increased the levels of
ATP and CrP and decreased the level of
lactate, whereas it further increased the levels of the
NEFA that had been elevated by
ischemia. The recovery of mechanical function was inversely correlated with the myocardial level of
arachidonic acid during
ischemia and reperfusion. We concluded that changes in the myocardial levels of
NEFA during
ischemia and reperfusion are different from those of
ATP, CrP, and
lactate, and suggest that the myocardial level of
arachidonic acid during
ischemia and reperfusion can be a sensitive and suitable marker for the recovery of mechanical function during reperfusion.