Valdivia H H, Kaplan J H, Ellis-Davies G C, Lederer W J
Department of Physiology, University of Maryland Medical School, Baltimore 21201, USA.
Science. 1995 Mar 31;267(5206):1997-2000. doi: 10.1126/science.7701323.
Channel adaptation is a fundamental feature of sarcoplasmic reticulum calcium release channels (called ryanodine receptors, RyRs). It permits successive increases in the intracellular concentration of calcium (Ca2+) to repeatedly but transiently activate channels. Adaptation of RyRs in the absence of magnesium (Mg2+) and adenosine triphosphate is an extremely slow process (taking seconds). Photorelease of Ca2+ from nitrophenyl-EGTA, a photolabile Ca2+ chelator, demonstrated that RyR adaptation is rapid (milliseconds) in canine heart muscle when physiological Mg2+ concentrations are present. Phosphorylation of the RyR by protein kinase A increased the responsiveness of the channel to Ca2+ and accelerated the kinetics of adaptation. These properties of the RyR from heart may also be relevant to other cells in which multiple agonist-dependent triggering events regulate cellular functions.
通道适应性是肌浆网钙释放通道（称为兰尼碱受体，RyRs）的一个基本特征。它允许细胞内钙（Ca2+）浓度的连续增加，以反复但短暂地激活通道。在没有镁（Mg2+）和三磷酸腺苷的情况下，RyRs的适应性是一个极其缓慢的过程（需要数秒）。从光不稳定的Ca2+螯合剂硝基苯基乙二醇双乙酸酯中光释放Ca2+表明，当存在生理浓度的Mg2+时，犬心肌中的RyR适应性很快（毫秒级）。蛋白激酶A对RyR的磷酸化增加了通道对Ca2+的反应性，并加速了适应性动力学。心脏中RyR的这些特性可能也与其他细胞相关，在这些细胞中，多种激动剂依赖性触发事件调节细胞功能。
