Halothane modulation of skeletal muscle ryanodine receptors: dependence on Ca2+, Mg2+, and ATP.
Halothane modulation of skeletal muscle ryanodine receptors: dependence on Ca2+, Mg2+, and ATP.
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氟烷对骨骼肌兰尼碱受体的调节：依赖于 Ca2 、Mg2 和 ATP。
DOI：
10.1152/ajpcell.90642.2007
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发表时间：
2008
期刊：
影响因子：
--
通讯作者：
Copello,JulioA
中科院分区：
文献类型：
--
作者：
Diaz-Sylvester,PaulaL;Porta,Maura;Copello,JulioA
恶性高热(MH)易感性是一种与肌浆网兰尼碱受体亚型1(RyR1)突变相关的骨骼肌遗传性疾病。在MH敏感的骨骼纤维中，RyR1介导的钙释放对挥发性麻醉剂氟烷的激活高度敏感。事实上，对分离的RyR1通道的研究(使用简单的Cs+溶液)发现，氟烷选择性地影响突变的但不影响野生型RyR1的功能。然而，对骨骼纤维的研究表明，氟烷也可以激活野生型RyR1介导的钙释放。我们假设内源性RyR1激动剂(ATP、腔内钙离子)可能增加RyR1对氟烷的敏感性。因此，我们研究了这些激动剂如何影响氟烷对重组为平面脂质双层的兔骨骼RyR1的作用。我们发现胞浆中的三磷酸腺苷是氟烷诱导骨骼RyR1激活所必需的。与RyR1不同，心脏RyR2(对ATP的敏感性低得多)对氟烷有反应，即使在没有这种激动剂的情况下也是如此。通道激动剂胞内Ca~(2+)可增强RyR1对ATP依赖的氟烷的激活作用，而通道抑制剂Mg~(2+)则能拮抗其激活作用。丹曲林是一种用于治疗MH发作的肌肉松弛药，它不影响RyR1或RyR2的基础活性，也不干扰氟烷诱导的激活。对骨骼肌质网微粒体的研究证实，氟烷诱导的RyR1介导的肌质网钙离子释放被胞浆中高ATP-低镁离子和增加肌质网钙负荷所增强。因此，引起这些调节剂细胞水平变化的生理或病理过程可能会影响RyR1对骨骼纤维中氟烷的敏感性，包括用于诊断MH敏感性的氟烷诱导收缩试验的结果。
Malignant hyperthermia (MH) susceptibility is a genetic disorder of skeletal muscle associated with mutations in the ryanodine receptor isoform 1 (RyR1) of sarcoplasmic reticulum (SR). In MH-susceptible skeletal fibers, RyR1-mediated Ca2+release is highly sensitive to activation by the volatile anesthetic halothane. Indeed, studies with isolated RyR1 channels (using simple Cs+solutions) found that halothane selectively affects mutated but not wild-type RyR1 function. However, studies in skeletal fibers indicate that halothane can also activate wild-type RyR1-mediated Ca2+release. We hypothesized that endogenous RyR1 agonists (ATP, lumenal Ca2+) may increase RyR1 sensitivity to halothane. Consequently, we studied how these agonists affect halothane action on rabbit skeletal RyR1 reconstituted into planar lipid bilayers. We found that cytosolic ATP is required for halothane-induced activation of the skeletal RyR1. Unlike RyR1, cardiac RyR2 (much less sensitive to ATP) responded to halothane even in the absence of this agonist. ATP-dependent halothane activation of RyR1 was enhanced by cytosolic Ca2+(channel agonist) and counteracted by Mg2+(channel inhibitor). Dantrolene, a muscle relaxant used to treat MH episodes, did not affect RyR1 or RyR2 basal activity and did not interfere with halothane-induced activation. Studies with skeletal SR microsomes confirmed that halothane-induced RyR1-mediated SR Ca2+release is enhanced by high ATP-low Mg2+in the cytosol and by increased SR Ca2+load. Thus, physiological or pathological processes that induce changes in cellular levels of these modulators could affect RyR1 sensitivity to halothane in skeletal fibers, including the outcome of halothane-induced contracture tests used to diagnose MH susceptibility.