Inhibition of Ca2+ entry by Ca2+ overloading of intracellular Ca2+ stores in human platelets.
Inhibition of Ca2+ entry by Ca2+ overloading of intracellular Ca2+ stores in human platelets.
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通过人血小板中细胞内 Ca2 储存的 Ca2 超载来抑制 Ca2 进入。
DOI：
10.1113/jphysiol.1994.sp020273
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发表时间：
1994
期刊：
影响因子：
--
通讯作者：
Aviv,A
中科院分区：
文献类型：
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作者：
Kimura,M;Cho,JH;Reeves,JP;Aviv,A
1. 本研究探讨了人血小板细胞内 Ca2+ 储存超载对激动剂诱发的外部 Ca2+ 进入速率的影响。为了使 Ca2+ 储存超载（可能是致密小管），通过用哇巴因或无 Na(+) 培养基预处理细胞来抑制通过 Na(+)-Ca2+ 交换的外部 Na(+) 依赖性 Ca2+ 外流。然后在暴露于凝血酶、ADP 和毒胡萝卜素后检查 Ca2+ 调节。使用荧光探针fura-2监测胞质游离Ca2+水平，并通过细胞外Mn2+或45Ca2+摄取率评估外部Ca2+流入。 2.哇巴因和无Na(+)预处理均导致静息胞质游离Ca2+略有增加。 3. 在含 1 mM Ca(2+) 的培养基中，Ca(2+) 超载的血小板表现出与对照血小板相似的凝血酶诱发的胞质游离 Ca2+ 反应。然而，在不含 Ca(2+) 的培养基中，它们表现出比对照血小板更大的凝血酶诱发的胞质游离 Ca2+ 反应。此外，凝血酶诱发的 Ca2+ 从 Ca2+ 储存位点动员的增加伴随着凝血酶诱发的外部 Ca2+ 进入速率的降低。 4. 用 ADP 和毒胡萝卜素治疗后，观察到外部 Ca2+ 进入速率的类似降低。 5. 蛋白激酶 C 抑制剂（钙磷蛋白 C 和星形孢素）未能逆转哇巴因预处理对凝血酶诱导的胞质游离 Ca2+ 反应变化的影响。 6. 哇巴因处理和未处理的血小板中的肌醇 1,4,5-三磷酸谱没有显着差异。 7. 这些数据表明，致密小管中 Ca2+ 的增加与激动剂引起的外部 Ca2+ 流入的减少有关。
1. This study examined the effect of overloading human platelet intracellular Ca2+ stores on the rate of agonist‐evoked external Ca2+ entry. To overload the Ca2+ stores (presumably dense tubules), external Na(+)‐dependent Ca2+ efflux via Na(+)‐Ca2+ exchange was inhibited by pretreating the cells with ouabain or Na(+)‐free medium. Ca2+ regulation was then examined after exposure to thrombin, ADP and thapsigargin. Cytosolic free Ca2+ levels were monitored using the fluorescent probe fura‐2 and external Ca2+ influx was assessed by the rates of extracellular Mn2+ or 45Ca2+ uptake. 2. Both ouabain and Na(+)‐free pretreatments caused a slight increase in the resting cytosolic free Ca2+. 3. In 1 mM Ca(2+)‐containing medium, Ca(2+)‐overloaded platelets showed similar thrombin‐evoked cytosolic free Ca2+ responses to those of control platelets. However, in Ca(2+)‐free medium, they showed substantially greater thrombin‐evoked cytosolic free Ca2+ responses than control platelets. Moreover, increased thrombin‐evoked Ca2+ mobilization from Ca2+ storage sites was accompanied by a diminished rate of thrombin‐evoked external Ca2+ entry. 4. Similar reductions in the rate of external Ca2+ entry were observed after treatment with ADP and thapsigargin. 5. Protein kinase C inhibitors (calphostin C and staurosporine) failed to reverse the effect of ouabain pretreatment on thrombin‐induced changes in the cytosolic free Ca2+ response. 6. Inositol 1,4,5‐trisphosphate profiles in ouabain‐treated and non‐treated platelets were not significantly different. 7. These data indicate that increased Ca2+ in the dense tubules is associated with diminished agonist‐evoked external Ca2+ influx.