Ponce-Hornos J E, Parker J M, Langer G A
Department of Medicine, University of California, School of Medicine, Los Angeles 90024-1760.
Am J Physiol. 1990 Mar;258(3 Pt 2):H880-6. doi: 10.1152/ajpheart.1990.258.3.H880.
A new calorimetry method has been developed to measure heat production from heart cell suspensions under continuous perfusion. The method is technically independent of the temperature at which the measurements are made, allows full control of the perfusion media, and is suitable for various biological preparations such as cells from diverse tissues, membrane vesicles, or skinned cells. The resting heat rate (Hr) measured at 18.5 degrees C in three different species (19.2 +/- 0.43, 12.8 +/- 0.56, and 9.4 +/- 0.52 mW/g dry wt for rat, guinea pig, and rabbit ventricular myocytes, respectively) agrees with that obtained with other methodologies such as oxygen consumption, thermopiles, and whole heart calorimetry. The Hr measurements showed an excellent correlation with the percentage of rod-shaped cells, indicating that rounded cells are metabolically inactive. Although the time course of the effect of increasing extracellular [K] was dependent on the species, the new steady level of Hr observed under higher extracellular [K] was significantly higher in all three species (+8.3 +/- 1.2, +9.5 +/- 4.0, and +9.3 +/- 2.7 mW/g dry wt for rat, guinea pig, and rabbit ventricular cells, respectively). This indicates that the commonly used "arrested-heart" preparation (with high extracellular [K]) for evaluation of basal metabolism most probably overestimates the real resting values. The present results also show that the wide range of resting metabolism reported in whole tissue is not due to cellular heterogeneity nor to myocyte interaction and supports the idea of an inverse relationship between resting metabolism and body weight or animal size across species.
一种新的量热法已被开发出来，用于测量连续灌注下心细胞悬液的产热情况。该方法在技术上与测量时的温度无关，能完全控制灌注介质，适用于各种生物制剂，如来自不同组织的细胞、膜囊泡或去皮细胞。在18.5摄氏度下，对三种不同物种测量的静息热率（Hr）（大鼠、豚鼠和兔心室肌细胞分别为19.2±0.43、12.8±0.56和9.4±0.52 mW/g干重）与通过其他方法（如耗氧量、热电堆和全心量热法）获得的结果一致。Hr测量结果与杆状细胞的百分比显示出极好的相关性，表明圆形细胞代谢不活跃。尽管细胞外[K]升高的效应随时间的变化过程因物种而异，但在较高细胞外[K]下观察到的新的Hr稳定水平在所有三个物种中均显著更高（大鼠、豚鼠和兔心室细胞分别为+8.3±1.2、+9.5±4.0和+9.3±2.7 mW/g干重）。这表明，常用的用于评估基础代谢的“停跳心脏”制剂（细胞外[K]高）很可能高估了实际的静息值。目前的结果还表明，全组织中报道的广泛的静息代谢范围既不是由于细胞异质性，也不是由于心肌细胞相互作用，并且支持了跨物种静息代谢与体重或动物大小之间存在反比关系的观点。
