心肌肥厚大鼠心肌肌浆网和核被膜ryanodine受体变化的研究

Alterations in ryanodine receptors in cardiac sarcoplasmic reticulum and nuclear envelope isolated from cardiac hypertrophic rats

目的 :观察心肌肥厚大鼠心肌肌浆网 ( sarcoplasmic reticulum,SR)和核被膜 ( nuclear envelope,NE)的 ryanodine受体 ( Ry R)的变化 ,进一步探讨心肌肥厚发生机制。方法 :采用腹主动脉缩窄术制作心肌肥厚模型。用差速离心和密度梯度离心法分离心肌 SR和 NE,用同位素标记配体研究 Ry R的动力学特征。结果 :心肌细胞 NE上也存在 Ry R,其最大结合 ( Bmax)为 SR的 1 / 68,而离解常数 ( Kd)为 SR的 61 %。与假手术组相比 ,术后 4周大鼠心肌显著肥厚 ,左室重量指数增加 4 4 % ,左心功能代偿性增加 ,心肌 SR的 Ry R最大结合增加2 0 % ,而 NE的该受体 Bmax则增加 1倍 ,SR与 NE的 Bmax比值显著降低 ( P<0 .0 1 ) ;Kd与对照组接近。结论 :大鼠心肌细胞 NE上存在低密度、高亲和 Ry R,心肌肥厚时心肌 SR和 NE的 Ry R均上调 ,而 NE的受体增加幅度更大 ,这些改变可能参与心肌肥厚时心功能代偿和核反应异常的发生。

Objective:To observe changes in ryanodine receptors (RyRs) in cardiac sarcoplasmic reticulum (SR) and nuclear envelope (NE) isolated from cardiac hypertrophic rats,and to explore the mechanism underlying cardiac hypertrophy.Methods:Cardiac hypertrophy was induced by abdominal aortic coarctation.Myocardial SR and NE were fractionated with velocity and isopycnic gradient centrifugation.RyRs were assayed with 3 H labeled ligand.Results:RyRs with maximal binding ( B max) and dissociating ratio ( Kd ) of 1/68 and 61% respectively also existed in myocardial NE.Four weeks after operation,significant cardiac hypertrophy developed with a compensated left ventricular function.The B max of RyRs in SR and NE increased by 20% and 100% respectively in hypertrophic myocardium compared with controls ( P <0 01).The Kd for 〔 3H〕 ryanodine binding to SR and NE was unchanged.Conclusions:There are RyRs in myocardial NE,with lower density and higher affinity than those in SR.Upregulation of RyRs in both SR and NE,and especially in NE,might be involved in the development of mycardial hypertrophy.