A chloride channel blocker prevents the suppression by inorganic phosphate of the cytosolic calcium signals that control muscle contraction.
A chloride channel blocker prevents the suppression by inorganic phosphate of the cytosolic calcium signals that control muscle contraction.
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DOI：
10.1113/jp279917
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发表时间：
2021-01
期刊：
影响因子：
--
通讯作者：
Brum G
中科院分区：
文献类型：
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作者：
Ferreira JJ;Pequera G;Launikonis BS;Ríos E;Brum G
有氧运动导致磷酸肌酸水解，增加细胞内无机磷酸盐（Pi）的浓度。Pi扩散到肌浆网（SR）中，在那里它被认为形成不溶性的Ca 2+盐，从而有助于损害Ca 2+释放。关于Pi入口路径的信息仍然缺乏。在两栖动物肌肉赋予亚型3的RyR通道，Ca 2+火花频率与Ca 2+负载的SR，可用于监测这个变量。我们研究了Pi对蛙透化纤维中Ca ~（2+）火花的影响。相对事件频率（f/fref）随着[Pi]的增加而上升，在5 mM时达到2.54±1.6，然后单调下降，在[Pi] = 80 mM时达到0.09±0.03。[Ca 2 +]SR的测量证实了在高[Pi]时与火花频率相关的下降。一个大的[Ca 2 +]SR浪涌后，观察到Pi去除。阴离子通道是Pi进入SR的假定途径。我们测试了氯通道阻断剂9-蒽甲酸（9AC）对Pi进入SR的影响。将400 μM 9AC应用于细胞质，火花频率无显著增加，并降低了Pi对该参数的影响。在高细胞质Mg 2+存在下，用2 mM 9AC处理纤维抑制Pi对[Ca 2 +]SR和火花频率的影响，直至55 mM Pi。这些结果表明，氯离子通道（或转运蛋白）提供了无机磷酸盐进入SR的主要途径，并证实它通过在SR内与Ca 2+积累和沉淀而损害Ca 2+释放，从而导致肌源性疲劳。
Fatiguing exercise causes hydrolysis of phosphocreatine, increasing the intracellular concentration of inorganic phosphate (Pi). Pi diffuses into the sarcoplasmic reticulum (SR) where it is believed to forms insoluble Ca2+ salts, thus contributing to the impairment of Ca2+ release. Information on the Pi entrance pathway is still lacking. In amphibian muscles endowed with isoform 3 of the RyR channel, Ca2+ spark frequency is correlated with Ca2+ load of the SR and can be used to monitor this variable. We studied the effects of Pi on Ca2+ sparks in permeabilized fibres of the frog. Relative event frequency (f/fref) rose with increasing [Pi] reaching 2.54±1.6 at 5 mM and then decreased monotonically, reaching 0.09±0.03 at [Pi] = 80 mM. Measurement of [Ca2+]SR confirmed a decrease correlated with spark frequency at high [Pi]. A large [Ca2+]SR surge was observed upon Pi removal. Anion channels are a putative path for Pi into the SR. We tested the effect of chloride channel blocker 9-anthracenecarboxylic acid (9AC) on Pi entrance. 400 μM 9AC applied to the cytoplasm produced a non-significant increase in spark frequency and reduced the Pi effects on this parameter. Fibre treatment with 2 mM 9AC in the presence of high cytoplasmic Mg2+ suppressed Pi effects on [Ca2+]SR and spark frequency up to 55 mM Pi. These results suggest that chloride channels (or transporters) provide the main pathway of inorganic phosphate into the SR and confirm that it impairs Ca2+ release by accumulating and precipitating with Ca2+ inside the SR, thus contributing to myogenic fatigue.