The interactions of platelet-derived mediators on isolated canine coronary arteries

The interactions of 5-hydroxytryptamine (5-HT) and a thromboxane A2 mimetic, U44069, were investigated on rings of canine coronary arteries. 5-HT (10(-8) - 10(-5) M) and U44069 (10(-9) - 10(-6) M) produce coronary vasoconstriction which is potentiated by indomethacin (3 X 10(-6) M). In the presence of 10(-9) M 5-HT, U44069-induced vasoconstriction is enhanced. Similarly, 10(-9) M U44069 enhances the effects of 5-HT. In both cases this potentiation is greatest in the presence of indomethacin. Synergism between the platelet-derived mediators could contribute to coronary vasospasm and myocardial ischaemia.