Marquez M T, Consolini A, Bonazzola P, Ponce-Hornos J E
Instituto de Investigaciones Cardiológicas, Facultad de Medicina, Universidad de Buenos Aires, CONICET, Argentina.
Acta Physiol Scand. 1997 Jul;160(3):229-33. doi: 10.1046/j.1365-201X.1997.00137.x.
Heart basal metabolism has been classically studied as the energy expenditure of those processes unrelated to mechanical activity and often measured by rendering the heart inactive using cardioplegic solutions (usually by increasing extracellular K concentration ([Kle]). In arterially perfused rat heart (at 25 degrees C), raising [K]e from 7 to 25 mM at a constant extracellular Ca concentration ([Ca]e) (0.5 mM), induced an increase in resting heat production (Hr) from 4.1 +/- 0.3 to 5.1 +/- 0.3 mol. wt g-1. Under 25 mM K additional increase in [Ca]e further increased Hr to 6.0 +/- 0.4, 7.0 +/- 0.4 and 8.3 +/- 0.9 mol. wt g-1 for 1, 2 and 4 mM Ca, respectively. While under 7 mM K perfusion Hr was not affected by 4 microM verapamil, under 25 mM K and 2 mM Ca 0.4 microM verapamil induced a decrease in Hr (-1.6 +/- 0.2 mol. wt g-1, n = 5, P < 0.001). Caffeine increased Hr under 0.5 mM Ca and 7 mM K perfusion (+0.32 +/- 0.06 and +1.19 +/- 0.25 mol. wt g-1 for 1 and 5 mM caffeine respectively), but under 25 mM K conditions Hr was not affected by caffeine 2 mM. Severe hypoxia decreased Hr under both 7 and 25 mM K (3.7 +/- 0.5 to 2.7 +/- 0.4 mol. wt g-1 and 7.0 +/- 0.4 to 2.2 +/- 0.5 mol. wt g-1, respectively) suggesting that the increased Hr associated with the verapamil sensitive fraction of heat released is associated to a mitochondrial mechanism. Therefore, the use of high [K]e overestimates basal values by increasing a verapamil sensitive fraction of the energy released. In addition, high [K]e modifies a caffeine sensitive energy component probably due to a depletion of caffeine-dependent Ca stores.
心脏基础代谢一直以来都被经典地研究为与机械活动无关的那些过程的能量消耗，并且通常通过使用心脏停搏液使心脏失去活性来测量（通常是通过增加细胞外钾浓度([Kle])）。在动脉灌注的大鼠心脏（25摄氏度）中，在细胞外钙浓度([Ca]e)（0.5 mM）恒定的情况下，将[K]e从7 mM提高到25 mM，导致静息产热(Hr)从4.1±0.3增加到5.1±0.3 mol·wt g-1。在25 mM钾的情况下，[Ca]e的进一步增加分别使1 mM、2 mM和4 mM钙时的Hr进一步增加到6.0±0.4、7.0±0.4和8.3±0.9 mol·wt g-1。虽然在7 mM钾灌注下，4 microM维拉帕米不影响Hr，但在25 mM钾和2 mM钙时，0.4 microM维拉帕米导致Hr降低（-1.6±0.2 mol·wt g-1，n = 5，P < 0.001）。咖啡因在0.5 mM钙和7 mM钾灌注下增加了Hr（1 mM和5 mM咖啡因时分别为+0.32±0.06和+1.19±0.25 mol·wt g-1），但在25 mM钾条件下，2 mM咖啡因不影响Hr。严重缺氧在7 mM和25 mM钾时均降低了Hr（分别从3.7±0.5降至2.7±0.4 mol·wt g-1和从7.0±0.4降至2.2±0.5 mol·wt g-1），这表明与维拉帕米敏感的产热部分相关的Hr增加与线粒体机制有关。因此，使用高[K]e会通过增加释放能量中维拉帕米敏感部分来高估基础值。此外，高[K]e可能由于咖啡因依赖性钙储备的耗竭而改变了咖啡因敏感的能量成分。
