EFFECT OF 764-3 ON AGGREGATION AND CALCIUM MOVEMENTS IN AEQUORIN-LOADED HUMAN PLATELETS
摘要
Washed human platelets were roaded with the Ca^2+-sensitive photoprotein, oequorin, using hypoosmotic shock treatment technique. Then aggregarion and cytoplasmic ionized calcium concentration ([Ca^2+]i) changes in response to collagen or thrombin were measured simultaneously in the aequorin-loaded human plarelets vrith a Platelet Ionized Calcium Aggregometer. 764-3, an active component isolated from the Chinest medicinal herb Salvia Milttorrhtza Bge, inhibited platelet [Ca^2+[i rise as well as aggregation evoked by collagen or thrombin in the presence of extracellular Ca^2+, After the extracellular Ca^2+ was removed by addition of EGTA, collagen or thrombin, causing no aggregation, still elicited platelet [Ca^2+]i rise which refletted Ca^2+ mobilization from intraplatelet stores. Under this condition, 764-3 could also suppres splatelet [Ca^2+]i rise. Analysis shows that 764-3 inhibits platelet Ca^2+ influx and Ca^2+ mobilization with similar potency, which accounts for its suppression of platelet [Ca^2+]i rise, and must contribute to its inhibition of platelet aggregation.