The effects of bepridil, certain properties of which suggest antagonism of calcium flux, were studied: 1.1. On arterial blood pressure and heart rate in unanesthetized dogs. 1.2. On coronary and systemic hemodynamics in anesthetized dogs. 1.3. On regional blood flow (R.B.F.) in the myocardium of anesthetized dogs either normal or experimentally ischemic from temporary and/or permanent coronary occlusion. 2. Bepridil in unanesthetised dogs does not cause any significant change in heart rate or systolic blood pressure. Both the mean and diastolic blood pressures increase at the end of the observation period 20 minutes after the second injection. 3. In contrast, bepridil in anesthetized dogs induces a fall in peripheral resistance together with a drop in arterial blood pressure without any alteration in cardiac output. Both heart rate and contractile force are decreased while coronary flow is increased. 4. In models of localized transitory myocardial ischemia, bepridil (1 mg . kg-1 I.V.) induces a general increase in absolute R.B.F., particularly causing a favourable redistribution of coronary blood to the endocardium in ischemic areas, as evidenced by the improved endocardium/epicardium irrigation ratio. These favourable effects disappear when the dose of bepridil (3 mg . kg-1) used in this a preparation induces a marked drop in blood pressure and consequently a fall in coronary perfusion. 5. In models of localized permanent myocardial ischemia, bepridil has no effects either on R.B.F. in healthy or ischemic areas, or on the endocardium/epicardium irrigation ratios in these two types of areas.
