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

The interactions of 5-hydroxytryptamine (5-HT) and a thromboxane A 2 mimetic, U44069, were investigated on rings of canine coronary arteries. 5-HT (10 −8−10 −5M) and U44069 (10 −9−10 −6M) produce coronary vasoconstriction which is potentiated by indomethacin (3 × 10 −6M). 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 coronory vasospasm and myocardial ischaemia.