[Effects of methyl protodioscin on [Ca2+]i and ATPase activity in cardiomyocytes and analysis of mechanisms].

OBJECTIVE: To study the effects of methyl protodioscin on the [Ca2+]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+ [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 [Ca2+]i in cardiomyocytes of the MPD group and dilthiazem group was no different. After treatment with 40 mmol x L(-1) KCl, [Ca2+] 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.