Montoya G José V, Sutachan Jhon-Jairo, Corrales Alexandra, Xu Fang, Blanck Thomas J J, Recio-Pinto Esperanza
Anesthesiology Department, New York University Medical Center, New York, NY 10016, USA.
Brain Res. 2008 Jun 5;1213:12-26. doi: 10.1016/j.brainres.2008.03.022. Epub 2008 Mar 21.
In SH-SY5Y cells we have shown that stimulation with high extracellular K+ ([K+]e) evokes a transient increase in cytoplasmic Ca2+ ([Ca2+]cyt) (K+on) that is triggered by the opening of voltage-dependent Ca2+ channels and followed by Ca2+ -induced Ca2+ release from the endoplasmic reticulum (Xu, F., Zhang, J., Recio-Pinto, E. and Blanck, T.J., Halothane and isoflurane augment depolarization-induced cytosolic CA2+ transients and attenuate carbachol-stimulated CA2+ transients, Anesthesiology, 92 (2000) 1746-56). The removal of high-[K+]e results in a second transient increase in [Ca2+]cyt (K+off) that is independent of extracellular Ca2+ (Corrales, A., Montoya, G.J., Sutachan, J.J., Cornillez-Ty, G., Garavito-Aguilar, Z., Xu, F., Blanck, T.J. and Recio-Pinto, E., Transient increases in extracellular K+ produce two pharmacological distinct cytosolic Ca2+ transients, Brain Res., 1031 (2005) 174-184). In this study we further characterize the properties of K+off. We found that K+off was detectable at near physiological temperatures (34-36 degrees C) but, depending on the level of [K+]e, it was undetectable or highly diminished at room temperature. In contrast, K+on was increased by lowering the temperature. Extracellular Na+ -replacement with K+ did not affect K+off, indicating that K+off was not generated by osmolarity changes. Replacement of extracellular Na+ with choline+ did not affect K+off, indicating that K+off did not result from activity changes of the plasma membrane Na+/Ca2+ exchanger. Caffeine decreased K+on but not K+off. CCCP (carbonyl cyanide m-chlorophenyl), a protonophore uncoupler that decreases mitochondrial Ca2+ uptake, decreased K+on but not K+off. CGP37157, an inhibitor of the mitochondria Na+/Ca2+ exchanger, decreased K+off when added alone but not when added simultaneously with CCCP. Clonazepam had similar effects as CGP37157. These findings indicate that the generation of K+off is strongly temperature-dependent and its pharmacology is distinct from the [Ca2+]cyt changes observed previously at room temperature.
在SH-SY5Y细胞中，我们已经表明，用高细胞外钾离子浓度（[K⁺]e）刺激会引起细胞质钙离子浓度（[Ca²⁺]cyt）的短暂升高（K⁺on），这是由电压依赖性钙离子通道的开放引发的，随后是内质网的钙离子诱导的钙离子释放（Xu, F., Zhang, J., Recio-Pinto, E.和Blanck, T.J.，氟烷和异氟烷增强去极化诱导的细胞质钙离子瞬变并减弱卡巴胆碱刺激的钙离子瞬变，《麻醉学》，92 (2000) 1746 - 56）。去除高[K⁺]e会导致[Ca²⁺]cyt的第二次短暂升高（K⁺off），这与细胞外钙离子无关（Corrales, A., Montoya, G.J., Sutachan, J.J., Cornillez-Ty, G., Garavito-Aguilar, Z., Xu, F., Blanck, T.J.和Recio-Pinto, E.，细胞外钾离子的短暂升高产生两种药理学上不同的细胞质钙离子瞬变，《脑研究》，1031 (2005) 174 - 184）。在本研究中，我们进一步表征了K⁺off的特性。我们发现K⁺off在接近生理温度（34 - 36摄氏度）时可检测到，但根据[K⁺]e的水平，在室温下它不可检测或显著降低。相反，K⁺on会随着温度降低而增加。用钾离子替代细胞外钠离子不会影响K⁺off，表明K⁺off不是由渗透压变化产生的。用胆碱⁺替代细胞外钠离子不会影响K⁺off，表明K⁺off不是由质膜钠/钙交换器的活性变化导致的。咖啡因降低K⁺on但不降低K⁺off。CCCP（羰基氰化物间氯苯腙），一种质子载体解偶联剂，可减少线粒体对钙离子的摄取，降低K⁺on但不降低K⁺off。CGP37157，一种线粒体钠/钙交换器的抑制剂，单独添加时会降低K⁺off，但与CCCP同时添加时则不会。氯硝西泮具有与CGP37157类似的作用。这些发现表明，K⁺off的产生强烈依赖于温度，并且其药理学特性与之前在室温下观察到的[Ca²⁺]cyt变化不同。
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