Redondo P C, Rosado J A, Pariente J A, Salido G M
Department of Physiology, University of Extremadura, 10071 Cáceres, Spain.
J Physiol Biochem. 2005 Dec;61(4):507-16. doi: 10.1007/BF03168376.
Intracellular free Ca2+ concentration ([Ca2+]c) is finely regulated by several mechanisms that either increase or reduce [Ca2+]c. Two different Ca2+ pumps have been described so far as the main mechanisms for Ca2+ removal from the cytosol, either by its sequestration into the stores, mediated by the sarco(endo)plasmic reticulum Ca2+-ATPase (SERCA) or by Ca2+ extrusion to the extracellular medium, by the plasma membrane Ca2+-ATPase (PMCA). We have used inhibitors of these pumps to analyze their Ca2+ clearance efficacy in human platelets stimulated by the physiological agonist thrombin. Results demonstrate that, after platelet stimulation with thrombin, activation of SERCA precedes that of PMCA, although the ability of PMCA to remove Ca2+ from the cytosol last longer than that of SERCA. The efficacy of SERCA and PMCA removing Ca2+ from the cytosol is reduced when the concentration of thrombin increases. This phenomenon correlates with the greater increase in [Ca2+]c induced by higher concentrations of thrombin, which further confirms that SERCA and PMCA activities are regulated by [Ca2+]c.
细胞内游离钙离子浓度（[Ca2+]c）受到多种机制的精确调控，这些机制可升高或降低[Ca2+]c。迄今为止，已发现两种不同的钙离子泵是将钙离子从细胞质中清除的主要机制，一种是通过肌浆（内质）网钙离子-ATP酶（SERCA）介导将钙离子隔离到储存库中，另一种是通过质膜钙离子-ATP酶（PMCA）将钙离子排到细胞外介质中。我们使用了这些泵的抑制剂来分析它们在生理激动剂凝血酶刺激的人血小板中的钙离子清除效率。结果表明，在血小板被凝血酶刺激后，SERCA的激活先于PMCA，尽管PMCA从细胞质中清除钙离子的能力比SERCA持续的时间更长。当凝血酶浓度增加时，SERCA和PMCA从细胞质中清除钙离子的效率会降低。这种现象与较高浓度凝血酶诱导的[Ca2+]c更大幅度升高相关，这进一步证实了SERCA和PMCA的活性受[Ca2+]c调控。
