肾性高血压大鼠肥大心肌的力速关系和收缩末期张力长度关系

THE FORCE-VELOCITY RELATION AND END SYSTOLIC TENSION-LENGTH RELATION OF HYPERTROPHIED MYOCARDIUM IN RENAL HYPERTENSIVE RATS

左肾动脉部分狭窄造成大鼠肾血管性高血压,研究高血压四周肥大心肌的力速关系,收缩末期张力长度关系(ESTLR)以及对细胞外高钙的反应。结果表明:(1)肥大心肌主动峰张力 PT 轻度增大,零负荷最大缩短速度 V_(max)明显减小,收缩时程 TPT 延长(P<0.01),力速曲线向下移位;(2)高血压组心肌 ESTLR 与对照相似,亦为非线性的指数曲线。回归参数a(总张力)、k(静息张力)、b(曲线曲率)和 L。(最大缩短程度)均无明显改变(P>0.05),(3)高钙灌流时,肥大心肌的反应(△PT,△V_(max)和△TPT)与对照间无显著差异(P>0.05)。上述结果提示:高血压心肌肥大早期基础力学性能的变化以力速分离现象为特征,此时心肌功能的异常可能与肌膜钙转运系统的功能状态无关;对于心肌收缩能力的这种慢性改变,心肌力学指标比 ESTLR 类参数更敏感。

Renovascular hypertension was induced in rats by left renal artery constric-tion.Force-velocity relation,end systolic tension-length relation(ESTLR)andresponses to high extracellular calcium were investigated in hypertrophied myo-cardium with 4-week hypertension.The results showed that(1)The myocardialhypertrophy was accompanied by increased peak active tension,decreased maximalvelocity of shortening and prolonged contraction duration(P<0.01).(2)The ESTLRin hypertrophied myocardium was similar to that in the control,fitted well by anexponential curve and did not show significant alterations in all its regressionparameters(P>0.05).(3)No significant difference about the responses to highextracellular calcium(4 mmol/L)was observed between the control and the hyper-trophied myocardium(P>0.05).It is concluded that the mechanical propeltiesof hypertrophied myocardium were characterized by a dissociation between forcedevelopment and velocity of shortening and possibly these contractile abnor-malities at the early stage of cardiac hypertrophy are not related to ability of calciumtransport in cardiac plasma membrane.The indexes of myocardial mechanicsare more sensitive to changes in contractility of hypertrophied myocardium ascompared with the parameters of ESTLR.