EXPERIMENTAL ISCHEMIC HEART-DISEASE - EFFECTS OF SYNTHETIC THROMBOXANE-A-2

Two milliliters of thromboxane A2 (TXA2) solution was perfused in the coronary arteries by the balloon catheter inserted through right common carotid artery in rabbits. TXA2 was converted from prostaglandin H2 (PGH2) with thromboxane A2 synthetase in platelet microsomes. Serial changes on the ECG and hypotension were observed first hour after the injection in nine out of 11 studied rabbits. Six out of the seven autopsied rabbits showed myocardial ischemia or necrosis histologically. But four control rabbits that were injected with 2 ml inactivated 1.0 μg TXA2 solution did not show any change. The changes on the ECG were dose-dependent in 1.0, 0.5, and 0.1, μg TXA2 solution. In addition, the ECG and the blood pressure changes by 1.0 μg TXA2 solution were suppressed by pretreatment of a non-specific antagonist of TXA2, phthalazinol (1 mg/kg). These findings support the concept that TXA2 is the principal active substance in the filtrate of aggregated platelets that induced acute myocardial ischemia and necrosis in rabbits in a previous experiment. © 1979.