Barclay J K, Gibbs C L, Loiselle D S
Basic Res Cardiol. 1979 Nov-Dec;74(6):594-603. doi: 10.1007/BF01907501.
Active stress, stress-time integral (STI) and total heat production of cat right ventricular papillary muscles were recorded during brief trains of isometric twitch contractions at muscle lengths less than or equal to optimal length. Individual muscles were subjected to a 10 degree C change in temperature, a change of stimulus frequency and the addition of isoprenaline sulphate (10(-7) mol. 1(-1). The STI-heat and stress-heat data were subjected respectively to linear and quadratic regression analyses. For both relations, the intercept (stress-independent heat) was unaffected by the frequency change, doubled by the temperature decrease and trebled by the addition of isoprenaline. None of the treatments had a significant effect on the first or second order coefficients of the stress-heat relation. The slope of the STI-heat relation was halved by lowering the temperature, increased 50% by the addition of isoprenaline and unaffected by stimulus frequency. Thus the energetic cost of a given stress increment was constant across conditions while that for a given STI increment was not. Stress is the better mechanical index of myocardial energy cost when the inotropic state is changing.
在猫右心室乳头肌等长收缩的短暂串刺激过程中，于肌肉长度小于或等于最佳长度时记录主动张力、张力 - 时间积分（STI）和总产热量。对每块肌肉进行10℃的温度变化、刺激频率变化以及添加硫酸异丙肾上腺素（10⁻⁷mol·L⁻¹）处理。STI - 热量和张力 - 热量数据分别进行线性和二次回归分析。对于这两种关系，截距（与张力无关的热量）不受频率变化影响，因温度降低而翻倍，因添加异丙肾上腺素而增至三倍。这些处理均未对张力 - 热量关系的一阶或二阶系数产生显著影响。降低温度会使STI - 热量关系的斜率减半，添加异丙肾上腺素会使其增加50%，而刺激频率对其无影响。因此，在不同条件下，给定张力增量的能量消耗是恒定的，而给定STI增量的能量消耗并非如此。当心肌收缩力状态发生变化时，张力是心肌能量消耗更好的力学指标。
