毛冬青甲素对血小板激活时钙流动的影响

本文采用钙荧光指示剂 quin-2定量测试法测定了静息血小板胞浆内游离钙浓度及血小板激活时胞浆内游离钙浓度的变化,并以已知的钙通道拮抗剂异搏定作为对照、观察毛冬青甲素对血小板胞浆内游离钙浓度的影响。结果发现毛冬青甲素、异搏定都明显抑制凝血酶引起的血小板胞外钙的内流,二者作用强度非常近似,但都不能抑制同等剂量凝血酶所引起的胞内贮存钙的释放。

英文摘要:

Ilexonin A is an effective compound isolated from Ilex pubescens Hook.et Arn.It has been used in the clinic to treat cardiovascular diseases such as cerebral embolism and myocardial infarction. Experimental studies have shown that it inhibited thrombosis,platelet adhesion,and platelet aggregation and 5-HT release induced by collagen,ADP or A23187 in vitro and in vivo.The inhibitory effect of platelet aggregation induced by A23187 was reduced by adding CaCl₂（1mM）to the medium.It suggests that the effects of llexonin A on platelet function are possibly related to calcium. The present experiments were designed to investigate the effects of Ilexonin A on thrombin- induced Ca²⁺fluxes of platelets,in which quin-2 was used to measure the cytoplasmic Ca²⁺concen- tration.The results indicated that the free calcium concentrations of resting platelets and the platelets activated by thrombin were 78.65±7.74 nM and 871.10±123.63 nM respectively.After adding EGTA（1mM）to the medium,the calcium concentrations reduced to 34.75±7.77 nM and 50. 86±7.44 nM.llexonin A and verapamil markedly inhibited the thrombin induced Ca²⁺influx.The IC50 was 76.8 μM and 67.5 μM respectively.But both had no effect on thrombin-induced Ca²⁺release from dense tubular system.It suggests that Ilexonin A acts most likely as a calcium slow channel blocker.

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