A stable non-prostaglandin inhibitor of platelet aggregation in human aorta intima extracts.

An inhibitor of platelet aggregation induced by adenosine diphosphate, collagen, adrenaline and thrombin is present in aorta intima extracts. The inhibitor is relatively stable and is not inactivated by prolonged incubation at 37 degrees C or 22 degrees C, but boiling for 15 seconds destroys it. It is not extracted by diethyl ether or chloroform, and is not affected by incubation with indomethacin or tranylcypromine. Platelet aggregation induced by arachidonic acid is not affected by this inhibitor. These results suggest that this inhibitor is not PGI2 (prostacyclin), a recently described potent anti-aggregatory agent generated by blood vessel microsomes.