ABSTRACT
In a study, the effects of protopine on human platelet aggregation and arachidonic acid metabolism via cyclooxygenase and lipoxygenase enzymes were examined. Platelet aggregation induced by various platelet agonists was strongly inhibited by protopine in a concentration-related manner. The IC50 values (µM) of protopine (mean +/– SEM) against: arachidonic acid; 12 +/– 2: ADP; 9 +/– 2: collagen; 16 +/– 2 and platelet aggregation factor; 11 +/– 1, were much less than those observed for aspirin. In addition, protopine selectively inhibited the synthesis of thromboxane A2 via cyclooxygenase pathway. In vivo, pretreatment with protopine (50-100 µM/kg) protected rabbits from the lethal effects of arachidonic acid (2 µM/kg) or platelet aggregation factor (11 µM/kg) in dose-dependent manner. Protopine (50-100 µM/kg) also inhibited carrageenan-induced rat paw oedema with a potency of three-fold as compared to aspirin.9
