细胞核CaMK和Calcineurin 对大鼠心肌肥厚发生的作用

目的:研究大鼠心肌肥厚时,钙依赖的蛋白激酶和蛋白磷酸酶在心肌细胞膜、细胞浆和细胞核的分布规律,以探讨核钙信号与核反应在心肌肥厚发生过程中的病理生理意义.方法:制备腹主动脉缩窄大鼠心肌肥厚模型,同位素32P掺入法分别测定心肌细胞核、细胞浆和细胞膜的蛋白激酶活性及用无机磷生成显色法测定其蛋白磷酸酶活性.结果:腹主动脉缩窄术后4周大鼠心肌显著肥厚,伴有明显的血液动力学异常.与正常对照组相比较,腹主动脉缩窄心肌肥厚组心肌细胞核钙调素蛋白激酶(CaMK)活性增加101.1%(P＜0.01),其膜的酶活性升高40.2%(P＜0.01),而胞浆的酶活性不变(P＞0.05);心肌细胞核钙调神经磷酸酶(Calcineurin)活性增加43.6%(P＜0.05),膜和胞浆中其活性增加无显著性(P＞0.05).正常组和腹主动脉缩窄心肌肥厚组心肌细胞CaMK和Calcineurin活性分布为核＞膜＞胞浆(P＜0.01).结论:腹主动脉缩窄心肌肥厚时核内钙依赖的CaMK和Calcineurin活性增加,提示压力超负荷时细胞核内钙调节的蛋白磷酸化和去磷酸化水平增高,可能在介导心肌肥厚的发生中起重要作用.

The roles of nuclear Ca2+/CaM dependent kinases and calcineurin on the development of myocardial hypertrophy in rat

Aim: To evaluate whether protein phosphorylation and dephosporylation in nuclei play roles in the development of myocardial hypertrophy, distribution of protein kinases and phosphatases in cell fractions were determined.Methods: The model of hypertensive rat was established by abdominal aortic constriction. Velocity and isopyknic gradient centrifugation was employed to fractionate rat myocardium to membrane, cytosole and nuclei. Enzymatic methods were employed to determine kinases and phosphatases.Results:Compare with control group, the activity of CaMK increased by 101.1%( P<0.01 ) and 40.16%( P<0.01 ) respectively in nuclear and membranous fractions, changed without significance in cytosolic fraction; the activity of calcineurin in nuclei increased by 43.57%,( P<0.05 ), lightly changed without significance in membranous and cytosolic fractions. Conclusion: Nuclear translocation of CaMK and calcineurin, might play important roles on overload induced cardiac hypertrophy.