Dolor R J, Hurwitz L M, Mirza Z, Strauss H C, Whorton A R
Department of Pharmacology, Duke University Medical Center, Durham, North Carolina 27710.
Am J Physiol. 1992 Jan;262(1 Pt 1):C171-81. doi: 10.1152/ajpcell.1992.262.1.C171.
We have investigated the role of the intracellular Ca2+ pool in regulating Ca2+ entry into vascular endothelial cells. The intracellular Ca2+ pool was mobilized using either thapsigargin (TG) or 2',5'-di(tert-butyl)-1,4-benzohydroquinone (BHQ), inhibitors of the endoplasmic reticulum Ca(2+)-adenosinetriphosphatase (ATPase). Mobilization of intracellular Ca2+ stores with either inhibitor depleted intracellular Ca2+ and greatly reduced subsequent mobilization of the inositol 1,4,5-trisphosphate (IP3)-sensitive intracellular Ca2+ pool by bradykinin. However, bradykinin-induced mobilization of the IP3-sensitive intracellular Ca2+ pool only partially reduced the subsequent response of cells to TG and BHQ. Mobilization of the intracellular Ca2+ pool by either TG or BHQ led to a concentration-dependent elevation of cytosolic Ca2+ concentrations ([Ca2+]i) without initiating inositol polyphosphate formation. In contrast to the rapidly developing, transient rise in Ca2+ concentration initiated by bradykinin, maximal concentrations of TG and BHQ stimulated a slowly developing, prolonged elevation of [Ca2+]i that required extracellular Ca2+ and could be blocked by extracellular Ni2+. Extracellular Ca2+ entered the cell through an activated cation entry pathway, since bradykinin, TG, and BHQ stimulated Mn2+ and 45Ca2+ entry. Bradykinin-stimulated 45Ca2+ uptake reached a peak within 2 min, whereas 45Ca2+ influx initiated by TG or BHQ continued for at least 8 min. Importantly, the [Ca2+]i response after low concentrations of BHQ was more transient than that seen after TG. The return of [Ca2+]i to basal values after low concentrations of BHQ was associated with reversal of Ca(2+)-ATPase inhibition and refilling of the IP3-sensitive Ca2+ pool. The continued elevation of [Ca2+]i and prolonged Ca2+ entry seen with TG was associated with continued Ca(2+)-ATPase inhibition and an empty IP3-sensitive Ca2+ pool. We conclude that mobilization of intracellular Ca2+ stores induces Ca2+ entry in endothelial cells which continues until the intracellular Ca2+ pool is refilled.
我们研究了细胞内钙库在调节钙离子进入血管内皮细胞过程中的作用。使用毒胡萝卜素（TG）或2',5'-二（叔丁基）-1,4-苯二酚（BHQ）来动员细胞内钙库，这两种物质都是内质网钙（2+）-三磷酸腺苷酶（ATPase）的抑制剂。用任何一种抑制剂动员细胞内钙库都会耗尽细胞内的钙离子，并极大地减少随后缓激肽对肌醇1,4,5-三磷酸（IP3）敏感的细胞内钙库的动员。然而，缓激肽诱导的IP3敏感细胞内钙库的动员仅部分降低了细胞随后对TG和BHQ的反应。TG或BHQ对细胞内钙库的动员导致胞质钙离子浓度（[Ca2+]i）呈浓度依赖性升高，且未引发肌醇多磷酸的形成。与缓激肽引发的快速发展的短暂钙离子浓度升高相反，TG和BHQ的最大浓度刺激了[Ca+]i的缓慢发展、持续升高，这需要细胞外钙离子，并且可以被细胞外镍离子阻断。细胞外钙离子通过激活的阳离子进入途径进入细胞，因为缓激肽、TG和BHQ刺激了锰离子和45钙离子的进入。缓激肽刺激的45钙离子摄取在2分钟内达到峰值，而TG或BHQ引发的45钙离子内流持续至少8分钟。重要的是，低浓度BHQ后的[Ca2+]i反应比TG后的反应更短暂。低浓度BHQ后[Ca2+]i恢复到基础值与钙（2+）-ATP酶抑制的逆转和IP3敏感钙库的重新填充有关。TG导致的[Ca2+]i持续升高和钙离子持续内流与钙（2+）-ATP酶的持续抑制和IP3敏感钙库的排空有关。我们得出结论，细胞内钙库的动员诱导内皮细胞中的钙离子进入，这种进入会持续到细胞内钙库重新填充。
