心肌细胞核Ca^(2+)-ATP酶活性特征的研究

CHARACTERISTICS OF MYOCARDIAL NUCLEAR Ca^(2+)-ATPase IN RABBIT

目的：观察心肌细胞核钙泵活性特征及核蛋白磷酸化对其活性的影响。方法：在密度梯度离心纯化的离体家兔心肌细胞核上进行实验，采用酶学方法测定Ca2+ATP酶活性。结果：心肌细胞核上存在Ca2+－ATPase，其活性具有〔Ca2+〕和〔ATP〕依赖性。蛋白激酶A（PKA）和蛋白激酶M（PKM）依赖的核蛋白磷酸化能显著抑制心肌细胞核Ca2+－ATPase活性，Vmax分别降低46％和44％，而Km分别降低47％和78％（P＜0.01）。结论：家兔心肌细胞核上存在高亲和力的钙泵，其活性受蛋白磷酸化调节，其生理和病理意义有待进一步探讨。

Objetive: To investigate myocardial nuclear Ca-ATPase and its regulation by proteinphosphorylation. Methods: Rabbit myocardial nuclei were isolated and purified with sucrose densitycentrifugation and the activity of Ca-ATPase was measured enzymologically. Results: The activity of myocardialnuclear Ca-ATPase was 〔Ca2+〕and 〔ATP〕dependent. Phosphorylation by PKA or by PKM inhibited theactivity of nuclear Ca-ATPase markedly. Conclusion: The findings illustrate that Ca-ATRase with high affinityto Ca+ and ATP is present in rabbit myocardial nuclei. The pathophysiological role of myocardial nuclear Ca-ATPase should to be further determined.