Ｅｌａｓｔａｓｅの血小板凝集および血小板アラキドン酸代謝に及ぼす影響について

Abstract

We studied ex vivo and in vitro effects of elastase on platelet aggregation and its arachidonic acid (AA) metabolism in normal aubjects. Aggregation of platelets in citrated plasma (PRP aggregation) and of washed platelets were nephelometrically studied and whole blood aggregation by the impedance method was also determined. Elastase showed the significant inhibitory effects on PRP aggregation induced by collagen (0.5μg/ml) and AA (increase in its threshold concentration) as well as on whole blood aggregation by collagen (2.0μg/ml) after its oral administration of 10, 800 units per day for a week in 8 volunteers. Plasma prostacyclin-regenerating activities were not affected throughout. In in vitro experiments, elastase inhibited washed platelet aggregation induced by AA, collagen and thrombin, and PRP aggregation induced by ADP, epinephrine and STA2 (a stable analog of thromboxane A2) was also inhibited. Elastase decreased TX B2 production by platelets incubated with collagen or thrombin as measured by a radioimmunoassay, but failed to inhibit its production by exogenous AA.Thus, it was demonstrated that elastase inhibited platelet aggregation in certain conditions ex vivo as well as in vitro and its mechanism seemed to be due to some inhibitory effects on the platelet membrane rather than through the inhibition of cyclo-oxygenase activities.