Abstract
The in vivo effectiveness of the thromboxane synthetase inhibitor OKY-1581 was tested in normal and infarcted canine myocardium. A rapid in vitro assay was developed which permits an accurate assessment of the status of the tissue thromboxane synthetase at the time of sacrifice. Reperfused infarcts were created by two hours of coronary artery occlusion followed by release of occlusion and three days of recovery. OKY-1581 was infused at 100 μg/kg/min for 15 minutes, a dose previously found to cause an 85% inhibition of canine platelet thromboxane synthetase in vivo . The heart was rapidly excised and transmural tissue plugs of infarcted and normal areas were obtained. These were incubated for 5 minutes with prostaglandin endoperoxide (PGH 2) in phosphate buffer. Thromboxane production was inhibited from 16 ± 1 ng TxB 2 per tissue plug to 5 ± 1 in normal myocardium and from 27 ± 5 to 6 ± 1 in infarcted areas of myocardium. Control incubations showed no further inhibition with the in vitro addition of 20 μg/ml OKY-1581, confirming the completeness of in vivo inhibition. Thus significant inhibition of thromboxane synthetase by intravenous OKY-1581 occurs even in a reperfused zone of infarction.
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