Depletion of the inositol 1,4,5-trisphosphate-sensitive intracellular Ca2+ store in vascular endothelial cells activates the agonist-sensitive Ca(2+)-influx pathway.
Depletion of the inositol 1,4,5-trisphosphate-sensitive intracellular Ca2+ store in vascular endothelial cells activates the agonist-sensitive Ca(2+)-influx pathway.
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DOI：
10.1042/bj2840521
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发表时间：
1992-06
期刊：
影响因子：
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通讯作者：
William P. Schilling;Olga A. Cabello;L. Rajan
中科院分区：
文献类型：
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作者：
William P. Schilling;Olga A. Cabello;L. Rajan
先前在非兴奋性细胞中的研究表明，内部Ca 2+储存的耗尽通过不需要刺激磷酸肌醇水解的机制激活来自细胞外空间的Ca 2+内流。为了在血管内皮细胞中验证这一假设，检测了Ca（2+）-ATP酶/泵抑制剂2，5-二叔丁基氢醌（BHQ）对细胞溶质游离Ca 2+浓度（[Ca 2 +]i）的影响。BHQ产生的[Ca 2 +]i的剂量依赖性增加，保持高于基础值几分钟，并在细胞外Ca 2+的情况下基本上受到抑制。缓激肽在BHQ后的应用表明，BHQ敏感隔室部分重叠缓激肽敏感储存。另外两种Ca（2+）-ATP酶抑制剂毒胡萝卜素和环匹阿尼酸也得到了类似的结果。虽然BHQ对磷酸肌醇水解没有影响，但该试剂刺激45 Ca 2+内流和外流。这些结果表明，激动剂敏感的Ca 2+库的耗尽足以激活Ca 2+内流。内贮耗竭激活的Ca（2+）内流途径的几个特征与激动剂激活的途径进行了比较。缓激肽刺激的Ca 2+内流在碱性细胞外pH（pHo）下增加，并被细胞外La 3+、膜去极化和新型Ca（2+）内流阻滞剂1-（β-[3-（4-甲氧基苯基）丙氧基]-4-甲氧基苯乙基）-1H-咪唑盐酸盐（SKF 96365）抑制。此外，缓激肽刺激流入的45 Ca 2+和133 Ba 2+，这与激动剂激活的流入途径是渗透这两个二价阳离子的假设一致。同样，激活的Ca 2+内流BHQ，毒胡萝卜素和cyclopiazonic酸被封锁的La 3+，膜去极化和SKF 96365，但不受尼群地平或BAY K 8644。碱性条件下，BHQ可增加~（45）Ca ~（2+）和~（133）Ba ~（2+）的内流，BHQ对~（45）Ca ~（2+）和~（133）Ba ~（2+）的内流的促进作用相同。这些结果表明，激动剂激活的Ca（2+）内流途径和激动剂敏感的内部Ca（2+）库耗尽激活的途径是不可区分的。
Previous studies in non-excitable cells have suggested that depletion of internal Ca2+ stores activates Ca2+ influx from the extracellular space via a mechanism that does not require stimulation of phosphoinositide hydrolysis. To test this hypothesis in vascular endothelial cells, the effect of the Ca(2+)-ATPase/pump inhibitor 2,5-di-t-butylhydroquinone (BHQ) on cytosolic free Ca2+ concentration ([Ca2+]i) was examined. BHQ produced a dose-dependent increase in [Ca2+]i, which remained elevated over basal values for several minutes and was substantially inhibited in the absence of extracellular Ca2+. Application of bradykinin after BHQ demonstrated that the BHQ-sensitive compartment partially overlapped the bradykinin-sensitive store. Similar results were obtained with thapsigargin and cyclopiazonic acid, two other Ca(2+)-ATPase inhibitors. Although BHQ had no effect on phosphoinositide hydrolysis, both 45Ca2+ influx and efflux were stimulated by this agent. These results suggest that depletion of the agonist-sensitive Ca2+ store is sufficient for activation of Ca2+ influx. Several characteristics of the Ca(2+)-influx pathway activated by internal store depletion were compared with those of the agonist-activated pathway. Bradykinin-stimulated Ca2+ influx was increased at alkaline extracellular pH (pHo), and was inhibited by extracellular La3+, by depolarization of the membrane, and by the novel Ca(2+)-influx blocker 1-(beta-[3-(4-methoxyphenyl)propoxy]-4- methoxyphenethyl)-1H-imidazole hydrochloride (SKF 96365). Additionally, bradykinin stimulated influx of both 45Ca2+ and 133Ba2+, consistent with the hypothesis that the agonist-activated influx pathway is permeable to both of these bivalent cations. Likewise, activation of Ca2+ influx by BHQ, thapsigargin and cyclopiazonic acid was blocked by La3+, membrane depolarization and SKF 96365, but was unaffected by nitrendipine or BAY K 8644. Furthermore, Ca2+ influx stimulated by BHQ was increased at alkaline pHo and BHQ stimulated the influx of both 45Ca2+ and 133Ba2+ to the same extent. These results demonstrate that the agonist-activated Ca(2+)-influx pathway and the pathway activated by depletion of the agonist-sensitive internal Ca2+ store are indistinguishable.