大鼠离体乳头肌收缩末期张力—长度关系的曲线性

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。

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

A series of isotonic tension, shortening and shortening velocity were obtained in isolated rat papillary muscles by varying the ++set point force against which the muscle 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 tension and b means curved degree and length-axis intercept (L0) represents maximal shortening. There was a greater correlation index R2 when fitted with the equation compared with linear regression (P less than 0.001). (2) High Ca2+]0 shifted ESTLR leftward and upward, with increased a, b and maximal shortening L0, so did norepinephrine (NE) but significantly less than high Ca2+]0, whereas the changes in rates of shortening and tension rise were greater during NE infusion than during high Ca2+]0 infusion. These results indicated that ESTLR was non-linear in isolated myocardium and exponential parameters a, b and L0 were sensitive to changes in contractile intensity, but less sensitive to changes in contractile velocity when compared with indexes of myocardial mechanics.