Qi X, Rouleau J L
Department of Medicine, Montréal Heart Institute, QC, Canada.
Can J Physiol Pharmacol. 1996 Oct;74(10):1166-70.
Rats in which ligation of the left anterior descending (LAD) coronary artery did not result in an infarct visible to the naked eye have generally been called sham-operated controls and have been used to evaluate changes in the characteristics of the remaining viable myocardium of rats where myocardial infarction was present. Whether these sham-operated rats are equivalent to normal controls or whether they have been altered by the surgery is unknown. The purpose of this study was to evaluate potential differences in papillary muscle mechanical characteristics and responsiveness to beta-adrenergic stimulation in control, open-chest, sham-operated (aborted infarct), and infarct rats 4 weeks after surgery. Absence of significant myocardial damage was verified by morphologic examination in sham-operated hearts: myocardial infarction scar was 1.5 +/- 0.6% (mean +/- SE) of circumference, no infarct being transmural. Basal contractile indices were decreased in papillary muscles in infarct rats compared with the three other groups. The response in contractile indices of infarct muscles to isoproterenol was also less compared with the other three groups. However, although basal contractility was the same in muscles from sham-operated, open-chest, and controls, the responsiveness of sham-operated muscles to isoproterenol was less: change in total tension of 2.9 +/- 1.2% vs. 9.5 +/- 2.7% for controls and 9.3 +/- 2.4% for open-chest (p < 0.05). Percent change in maximum rate of tension development (+dT/dt) was also less in muscles from sham-operated versus control muscles (21 +/- 2 vs. 33 +/- 6%; p < 0.05). Twitch configuration changed similarly with isoproterenol in all four groups. Thus, although contractility is unaffected by sham operation, beta-adrenergic responsiveness of tension-generating indices is modified.
左前降支（LAD）冠状动脉结扎后未出现肉眼可见梗死灶的大鼠通常被称为假手术对照组，并已被用于评估存在心肌梗死的大鼠剩余存活心肌特征的变化。这些假手术大鼠是否等同于正常对照组，或者它们是否已因手术而发生改变尚不清楚。本研究的目的是评估术后4周时，对照、开胸、假手术（梗死未形成）和梗死大鼠乳头肌机械特性以及对β-肾上腺素能刺激反应性的潜在差异。通过形态学检查证实假手术心脏无明显心肌损伤：心肌梗死瘢痕占圆周的1.5±0.6%（平均值±标准误），无透壁梗死。与其他三组相比，梗死大鼠乳头肌的基础收缩指标降低。梗死肌肉对异丙肾上腺素的收缩指标反应也低于其他三组。然而，尽管假手术、开胸和对照组肌肉的基础收缩力相同，但假手术肌肉对异丙肾上腺素的反应性较低：总张力变化为2.9±1.2%，而对照组为9.5±2.7%，开胸组为9.3±2.4%（p<0.05）。假手术肌肉与对照肌肉相比，最大张力发展速率（+dT/dt）的百分比变化也较小（21±2对33±6%；p<0.05）。在所有四组中，异丙肾上腺素引起的抽搐形态变化相似。因此，尽管假手术不影响收缩力，但产生张力指标的β-肾上腺素能反应性会发生改变。
