We evaluated the coronary vasoconstrictory action of intracoronary (i.c.) leukotriene D
4 (LTD
4) in anesthetized mongrel dogs (n=20) . Coronary blood flow (CBF), coronary arterial pressure (CAP), left ventricular enddiastolic pressure (LVEDP), aortic flow (AoF), coronary vascular resistance (CVR), and ST deviation on epicardial ECG were measured. Coronary sinus blood samplings were obtained in order to determine the influence of LTD
4 on prostanoids metabolism. In addition, to calarify whether the vasoconstrictory action of LTD
4 is primary or mediated by thromboxane A
2 (TXA
2), LTD
4 were administered after intravenous infusion of OKY-046 (a selective TXA
2 synthetase inhibitor) . Furthermore, to confirm the LTD
4-induced coronary spasm, coronary angiography (CAG) was performed. In results, LTD
4 0.33μg i.c. administration caused a significant reduction of CBF (from 0.85±0.05 to 0.66±0.06m
l/kg/min. mean±SEM, P<0.01) and a significant elevation of CVR (from 4.7±0.4 to 7.3±0.9×10
3 dynes⋅sec⋅cm
-5, P<0.05) concomitant with a marked elevation of ST segment on epicardial ECG (peak voltage 1.8±0.2mv, duration time 46±6sec) . LVEDP elevated significantly (from 8.7±0.6 to 9.7±0.7 mmHg, P<0.01), meanwhile, AoF and coronary sinus thromboxane B
2 (TXB
2) level were not changed. OKY-046 did not influence these changes induced by LTD
4. Furthermore, LTD
4-induced coronary spasm was directly documented by CAG. It was concluded that the coronary vasoconstrictory action of LTD
4 is independent of TXA
2 and may play an important role in the pathogenesis of coronary spasm and ischemic heart disease.
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