Abstract
Summary
1. Increased plasma levels of transaminase as well as aldolase, isomerase and “malic acid dehydrogenase7' activity occurred in dogs after experimental myocardial infarction and in humans suffering from coronary occlusion. 2. Plasma levels of all enzymes were highest 24 hours after experimental myocardial embolization and had fallen rapidly at 48 hours. 3. Normal human values for plasma isomerase and “malic acid dehydrogenase” were significantly lower than those found in normal dog plasma, 4. In dogs following experimental myocardial embolization plasma transaminase, “malic acid dehydrogenase” and aldolase were increased to a greater extent than isomerase. In humans the plasma aldolase activity was comparatively less elevated than that of transaminase, “malic acid dehydrogenase” and isomerase. In both man and dog, coronary occlusion resulted in comparable increases of plasma transaminase and “malic acid dehydrogenase” activity. In dogs with coronary embolism, there was a reversible decrease in coronary flow myocardial oxygen usage, coronary vascular resistance as well as an early reversible negative pyruvate balance. At 24 hours the coronary flow and myocardial oxygen usage had returned to normal. 5. The negative myocardial pyruvate balance appeared to be an immediate response of an hypoxic myocardium. In contrast, the release of enzymes into the plasma was correlated with muscle necrosis. 6. A rapid and simple method is described for the determination of “malic acid dehydrogenase” activity in plasma.
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