大鼠离体乳头肌收缩末期张力-长度关系的曲线性

THE CURVILINEARITY OF THE END SYSTOLIC TENSION-LENGTH RELATION OF ISOLATED RAT PAPILLARY MUSCLES

大鼠离体左室乳头肌固定于最适初长位,逐步递减“后荷”获得一系列等张收缩的张力、长度缩短程度和速度。结果发现:(1)收缩末期张力-长度关系(ESTLR)为指数曲线,回归方程 T=ar^(-bL)-K 拟合的优度明显高于线性方程拟合的优度(P<0.001),其中 a,k 分别代表总张力和静息张力,b 为曲线的弯曲度;(2)在高钙(4mmol/L)或去甲肾上腺素(NE10^(-6)mol/L)作用下,ESTLR 右上移位,a,b 和无张力缩短速度 L_O 均增大(P均<0.01),尤以高钙时的变化更明显,(3)NE 使张力-速度曲线的右上移位比高钙显著。这提示大鼠离体心肌的 ESTLR 呈非线性特征,参数 a,b 及长度轴截距 L_O 对收缩强度的变化敏感,但对收缩速度改变的敏感性可能比经典的力学指标低。

A series of isotonic tension,shortening and shortening velocity were obtainedin isolated rat papillary muscles by varying the setpoint force against which themuscle shortened at optimal length.It was found that(1)end systolic tension-length relation(ESTLR)could be described by an exponential equation.T=ae^(-bL)—k,where a and k represent respectively the total tension and the resting ten-sion and b means curved degree and length-axis intercept(L_0)represents maximalshortening.There was a greater correlation index R^2 when fitted with the equa-tion compared with linear regression(P<0.001).(2)High[Ca^(2+)]_0 shifted ESTLRleftward and upward,with increased a,b and maximal shortening L_0,so did nor-epinephrine(NE)but significantly less than high[Ca^(2+)]_0,whereas the changesin rates of shortening and tension rise were greater during NE infusion than duringhigh[Ca^(2+)]_0 infusion.These results indicated that ESTLR was non-linear inisolated myocardium and exponential parameters a,b and L_0 were sensitive tochanges in contractile intensity,but less sensitive to changes in contractilevelocity when compared with indexes of myocardial mechanics.