甲基原薯蓣皂苷对心肌细胞内钙及ATP酶功能的影响及其机制

目的:研究甲基原薯蓣皂苷(MPD)对大鼠心肌细胞内钙浓度(Ca2+]i)的活动及细胞膜ATP酶功能的影响,并分析其机制。方法:将乳鼠心肌细胞悬液随机分为对照组、MPD组、地尔硫卓(Dil)组,荧光分光光度计法观察心肌细胞Ca2+]i的变化。将培养的乳鼠心肌细胞分为对照组和MPD组,分别检测心肌细胞膜ATP酶活性,并观察肌浆网钙ATP酶SERCA2a基因的mRNA表达水平。结果:在静息状态下,各组的心肌细胞Ca2+]i均无显著性差异。但在KCl刺激下,MPD和Dil组与对照组相比,荧光信号峰值和Ca2+]i浓度均低于对照组(P0.001)。在心肌细胞膜ATP酶的活性中,MPD组的Na+-K+-ATP酶和Ca2+-Mg2+-ATP酶的活性显著高于对照组(P0.05,P0.01),而Mg2+-ATP酶的活性在2组间的比较无差异性。MPD组与对照组2组SERCA2a的mRNA表达量也无差异性。结论:MPD在一定程度上可以抑制细胞膜上电压依赖型钙通道开放,减少钙离子内流。MPD还可以通过提高心肌细胞膜钠泵和钙泵功能,影响心肌细胞钙离子跨膜转运,维持细胞内低钙离子的环境。

Effects of methyl protodioscin on i and ATPase activity incardiomyocytes and analysis of mechanisms

Objective :To study the effects of methyl protodioscin on the _i and the ATPase activity in cardiomyocytes, as well as their mechanisms. Method :The cardiomyocytes were randomly divided into three groups, the control group treated with no serumal DMEM, the MPD group treated with MPD and the dilthiazem group treated with dilthiazem. Fluorospectrophotometer was used to determined the level of myocardial cell intracellular Ca²⁺ _i. In the experiment of ATPase activity on cellular membrane, the cardiomyocytes were randomly divided into two groups, the control group treated with no serumal DMEM, the MPD group treated with MPD. The activity of Na⁺-K⁺-ATPase,Ca²⁺-Mg²⁺- ATPase and Mg²⁺-ATP ATPase were determined. The quantitative analysis of SERCA2a mRNA expression was studied by RT-PCR that the groups and treatments in cardiomyocytes same as the experiment for ATPase activity assay. Result : Under the quiescent condition, compared to the control group, the level of _i in cardiomyocytes of the MPD group and dilthiazem group was no different. After treatment with 40 mmol· L^-1 KCl, _i was significantly lower in the MPD group and the dilthiazem group, and the intensity of peak value in time course of 60 s, the dilthiazem group and the MPD group also were lower than the control group (P<0.001). Ca²⁺-Mg²⁺-ATPase and Na⁺-K⁺- ATPase in cultured rat were increased after treated with MPD compared to treatment with no serumal DMEM(P<0.05, P<0.01), but Mg²⁺-ATPase in these groups had no different. The expression of SERCA2a mRNA between the MPD group and the control group was no different. MPD could not up-regulated or down-regulated SERCA2a in endocytoplasmic reticulum. Conclusion : Methyl protodioscin could block the volt dependent form calcium channel in cellular membrane, and up-regulate the function of sodium pump and calcium pump, so that it could remain low calcium in the internal environment in cardiomyocytes.