Heart disease is the greatest killer and crippler of mankind. Despite the availability of sophisticated hospital facilities, i.e., Coronary Care Units, it has become abundantly clear that most patients die of heart attacks prior to their arrival at the hospital or shortly thereafter, i.e., it is the early stages of a heart attack - the acute necrosis or repair phases - toward which we must direct our attention. Two of the most vital complications which portend a good or bad prognosis are the presence or absence of pre-existing hypertension and arteriosclerosis. The applicants are dedicated to the multi-disciplinary approach, utilizing basic science and experimental techniques applied to problems in clinical cardiology. Acute myocardial infarction will be induced in rats with and without pre-existing arteriosclerosis or hypertension. Correlation will be made of the dynamic pathophysiologic changes which occur during the acute ischemia, necrosis and repair phases of myocardial infarction, i.e., gross and microscopic pathology of the heart, ECG, blood pressure, serum enzymes, e.g., CPK, glucose, lipids, e.g., triglycerides, etc. Correlation will be made of these changes as they relate to the presence or absence of hypertension and arteriosclerosis, and to the degree of heart damage as well as the course of the infarct. Special emphasis will be made of the early changes of myocardial damage and where the damage occurs, as well as why males are more susceptible to heart damage than females, and whether certain hormones, e.g., estrogens, androgens, prolactin, adrenal stress hormones, etc., may be helpful or detrimental to the outcome of myocardial infarction.