Membrane depolarization inhibits thrombin‐induced calcium influx and aggregation in human platelets

[摘要]

The relationship between thrombin-evoked changes in intracellular calcium concentration ([Ca²⁺]_i) and aggregation was examined in Indo-1-loaded human platelets. The stimulus-induced intracellular calcium release and external calcium influx, as well as platelet aggregation, were studied in the same cell preparation. A close correlation between the sustained high [Ca²⁺]_i level, depending on calcium entry, and the aggregation response was found. Gramicidin, at a concentration high enough to induce membrane depolarization, strongly inhibited the calcium influx and aggregation, but did not influence the thrombin-induced intracellular calcium release. We conclude that calcium influx through depolarization-inhibited calcium channels is a prerequisite of thrombin-induced platelet aggregation.

[学科分类] 生物化学/生物物理

[关键词] Human platelet;Aggregation;Thrombin;Calcium flux;Receptor-operated calcium channel;Membrane potential;BSA;bovine serum albumin;[Ca2+]i;intracellular free Ca2+ concentration;[Ca2+]o;extracellular free Ca2+ concentration;diS-C3-(5);3;3′-dipropylthiodicarbocyanine;EGTA;ethylene-glycol-bis-(2-aminoethyl ether)-N;N;N′;N′-tetraacetic acid;Hepes;4-(2-hydroxyethyl)- 1-piperazine-ethanesulfonic acid;Indo-1/AM;acetoxy-methylester of Indo-1