Isoproterenol-lnduced Myocardial Infarction in Rats

Mature male rats with isoproterenol-induced myocardial infarction and normal controls were injected intravenously with [1, 2-H] corticosterone (H corticosterone). Blood and tissue samples (liver, brain, adrenal glands, "normal" and necrotic areas of the heart) were collected 15, 30, and 45 minutes after tracer injection. Gross and histopathological changes were noted. The metabolic clearance rate of corticosterone was greater for the experimental group (11.9 liter/day) than in the normal group (8.4 liter/day). The production rate of corticosterone was approximately 4.45 mg/day for both groups of animals. The percent serum protein-binding of corticosterone was lowered from a normal of 70.3 to 56.7 in the group with cardiac necrosis. The data indicated that during myocardial infarction there was a decrease in the synthesis or availability of the corticosteroid-binding globulin. The increased uptake of H corticosterone by the adrenal glands reflected the increased adrenal glandular steroid metabolism as well as depletion of its corticosterone reserve in animals during the stress of cardiac necrosis. There was a greater uptake of H corticosterone by the hearts and brains of the animals with myocardial infarction; but during the acute phase of infarction, there was no selective uptake of H corticosterone by necrotic vs. normal-appearing areas of the heart. ADDITIONAL