Lack of involvement of thromboxane A2 in postischemic recovery of stunned canine myocardium

Modification of the thromboxane: prostacyclin ratio alters the severity of reperfusion arrhythmias and postischemic damage in long-term, irreversibly injured myocardium. In this study, the effects of the thromboxane synthetase inhibitor dazmegrel and the thromboxane receptor antagonist BM 13.505 on myocardial postischemic functional recovery and preservation of tissue adenine nucleotides was examined after a 15-minute episode of ischemia followed by 3 hours of reperfusion (myocardial stunning). Dazmegrel (3 or 8 mg/kg) or BM 13.505 (10 mg/kg) was given 15 minutes before coronary occlusion and compared with a control group in barbital-anesthetized dogs. Regional segment shortening (percent segment shortening, sonomicrometry), regional myocardial blood flow (microspheres), and coronary venous eicosanoid and high-energy phosphate levels (biopsies after 3 hours of reperfusion) were measured. Areas at risk, regional myocardial blood flow, and regional segment shortening during coronary occlusion were similar in all groups. Dazmegrel (3 mg/kg) attenuated the decrease in endocardial and midmyocardial adenosine 5'-triphosphate, and both doses significantly improved regional segment shortening during reperfusion. Coronary venous thrombo...Continue Reading