Ware J A, Johnson P C, Smith M, Salzman E W
Circ Res. 1986 Jul;59(1):39-42. doi: 10.1161/01.res.59.1.39.
Calcium antagonists inhibit platelet aggregation, but whether this action is due to inhibition of the effect of agonists on cytoplasmic ionized calcium concentration is unknown. We studied this problem by loading gel-filtered platelets with either quin2 or aequorin and stimulating them with epinephrine, arachidonate, thrombin, the calcium ionophore A23187, 1-oleoyl-2-acetyl glycerol, or adenosine diphosphate in media with or without extracellular calcium. In response to all of these agonists, aequorin indicated an increase in cytoplasmic calcium that accompanied or preceded platelet aggregation. In calcium-containing media, verapamil, nifedipine, and diltiazem inhibited these effects in a concentration-dependent fashion, except for those produced by thrombin and A23187. Removal of extracellular calcium with EGTA reduced the calcium response to arachidonate, adenosine diphosphate, and 1-oleoyl-2-acetyl glycerol, and the calcium response and aggregation were further inhibited by the calcium antagonists. In general, strong inhibition of the aequorin cytoplasmic calcium signal by approximately 100 microM concentrations of nifedipine, verapamil, and diltiazem was correlated with inhibition of platelet aggregation, but high concentrations of the inhibitors were required. Since inhibition by the calcium antagonists of the cytoplasmic calcium response and aggregation exceeded the effect of simple removal of extracellular calcium, these drugs may affect internal redistribution of calcium in human platelets.
钙拮抗剂可抑制血小板聚集，但这种作用是否归因于对激动剂作用于细胞质游离钙浓度的抑制尚不清楚。我们通过用喹2或水母发光蛋白加载凝胶过滤的血小板，并在有或没有细胞外钙的培养基中用肾上腺素、花生四烯酸、凝血酶、钙离子载体A23187、1-油酰-2-乙酰甘油或二磷酸腺苷刺激它们来研究这个问题。对所有这些激动剂的反应中，水母发光蛋白显示细胞质钙增加，伴随或先于血小板聚集。在含钙培养基中，维拉帕米、硝苯地平和地尔硫卓以浓度依赖的方式抑制这些作用，但凝血酶和A23187产生的作用除外。用乙二醇双四乙酸（EGTA）去除细胞外钙可降低对花生四烯酸、二磷酸腺苷和1-油酰-2-乙酰甘油的钙反应，并且钙拮抗剂进一步抑制钙反应和聚集。一般来说，约100微摩尔浓度的硝苯地平、维拉帕米和地尔硫卓对水母发光蛋白细胞质钙信号的强烈抑制与血小板聚集的抑制相关，但需要高浓度的抑制剂。由于钙拮抗剂对细胞质钙反应和聚集的抑制超过了简单去除细胞外钙的作用，这些药物可能会影响人血小板中钙的内部分布。
