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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。
Objective: To observe the characteristics of nuclear calcium pump activity of cardiac myocytes and the effect of nuclear protein phosphorylation on its activity. Methods: Experiments were performed on the myocardial nuclei of isolated rabbit hearts purified by density gradient centrifugation. The activity of Ca2 + ATPase was determined by enzymatic method. Results: There was Ca2 + -ATPase in the nucleus of myocardial cells, and its activity was [Ca2 +] and [ATP] dependent. Protein kinase A (PKA) and protein kinase M (PKM) -dependent nuclear protein phosphorylation significantly inhibited nuclear Ca2 + -ATPase activity in myocardium with Vmax decreased by 46% and 44%, respectively, whereas Km decreased by 47% and 78%, respectively (P < 0.01). CONCLUSION: There is a high-affinity calcium pump on the nucleus of rabbit myocardial cells, whose activity is regulated by protein phosphorylation. Its physiological and pathological significance needs to be further explored.