长期模拟失重大鼠心肌收缩性能的改变

应用在体及离体实验对一批悬吊90d大鼠的心肌收缩性能进行了观察。在体实验结果表明：悬吊组大鼠左室舒张本压及主动脉血压与对照组无显著性差别（P＞0．05）；但悬吊组大鼠左心室内压峰值较对照组降低16％（P＜0．01），左心室内压最大上升速率与最大下降速率也分别较对照组减慢28％（P＜0．05）与21％（P＜0．05）。对同一批大鼠的离体乳头肌，又用等长收缩灌流技术观察了力学特性变化。结果是：反映心肌收缩强度的指标，如最大发展张力（DT），在两组间无显著差别；反映心肌收缩速度的指标，如最大张力发展速率对DT的校正值，悬吊组较对照组降低了17．2％（P＜0．05）；反映收缩时程的指标，如悬吊组的至峰张力收缩时间与至峰张力发展速率收缩时间分别较对照组延长了12．7％（P＜0．01）和22．2％（P＜0．05）；反映心肌舒张的时程指标，如张力下降一半时间与至峰张力下降速率舒张时间分别较对照组延长183％（P＜0．01）与20．3％（P＜0．01）。以上结果表明，长期模拟失重大鼠心肌收缩性能明显降低，并主要表现为心肌收缩速率减慢和收缩与舒张时程延长。

Changes of myocardial contractility in rats after long-term simulated weightlessness

The myocardial function of 90-day tail-suspended rats were investigated both in vivo andin vitro,comparing with the pair-fed controls. In tail-suspended rats peak left ventricular pressure,peakrate of left ventricular pressure rising, and peak rate of left ventricular pressure decline of heart in sitewere remarkably lowered than those of control group,while no obvious changes were found in left ventricular end-diastolic pressure and aortic blood pressure. As to the isolated papillary muscles from thesesuspended rats,isometric time to peak tension,time to half relaxation,time to peak rate of tension risingand time to peak rate of tension decline were found to be obviously prolonged. A significant depressionin the velocity of tension rising normalized for peak tension was also observed in the tail-suspendedgroup. However, muscles from tail-suspended animals still possessed normal level of peak isometrictension deveoped from equivalent cross sectional area at the Lmax. The results indicate that longtermsimulated weightlessness may result in marked lowering of contractility of myocardium in rats.