钠、钾离子对肌质网囊泡NADH氧化酶和伴生超氧自由基的调控

Modulation of NADH Oxidase Activity and Associated Superoxide Production Rate in Skeletal Sarcoplasmic Reticulum Vesicles by Na^+ and K^+

目的探讨Na+、K+浓度对骨骼肌肌质网囊泡氧化还原系统的调控作用及对Ca2+释放通道的影响。方法提取肌质网囊泡,分别检测其在不同Na+、K+浓度下还原型辅酶Ⅰ(nicotinamideadeninednucleotide,NADH)氧化初速率、超氧产率、[3H]-ryanodine结合率和Ca2+释放速率的变化。结果高浓度的Na+、K+对肌质网NADH的氧化初速率和伴生的超氧自由基产率均有抑制作用;在[3H]-ryanodine结合实验中,高浓度的Na+、K+也压抑了NADH诱导的受配体结合的升高;同样,在Ca2+释放动力学实验中,不同浓度的K+调控了由NADH诱导的Ca2+释放初速率。结论骨骼肌肌质网膜上可能存在具有对Na+、K+浓度敏感并中介超氧自由基产生的NADH氧化还原系统,其参与调节Ca2+释放通道的活性。

Objective To determine whether the effect of nicotinamide adenine dinucleotide（NADH） on activation of the RyR1 are Na^＋ and K^＋ concentration dependent. Method Isolated sarcoplasmic reticulum （SR） vesicles were used, initial rate of NADH oxidation, production of superoxide, [^3H]- ryanodine binding rate, and Ca^2＋ release rate were detected respectively in different Na^＋ and K^＋ concentrations. Result It was found that the initial rate of NADH oxidation by SR and the production of superoxide were depressed at higher concentrations of Na^＋ and K^＋ , which implicated a salt ion concentration dependent mechanism. The [^3H]-ryanodine binding assays showed that the activations of RyR1 induced by NADH were depressed at higher salt concentrations. The initial rates of Ca^2＋ release were also modulated by different concentrations of K＋. Conclusion There is a NADHdependent oxidase on SR, which is modulated by Na^＋ and K^＋. It can generate superoxide, and in turn, regulates the activation of the RyR1.