Sagisaka K, Tamura M, Yamazaki I
J Biochem. 1984 Apr;95(4):1091-103. doi: 10.1093/oxfordjournals.jbchem.a134697.
From experiments at various perfusion pressures in hemoglobin-free perfused rat hearts, oxygen consumption and redox shift of pyridine nucleotide were found to vary linearly with cardiac work. This relation was used for analysis of the energy metabolism associated with ion pumps. Mechanical activities such as left ventricular pressure and heart rate varied with the extracellular K+ concentration. Ion-pump dependent changes in oxygen consumption and redox state of pyridine nucleotide, estimated as the difference of the values at normal (4.7 mM) and various other extracellular K+ concentrations with corrections for the change due to mechanical work, were found to vary linearly with the K+ concentration. The slope for oxygen consumption was about 0.1 mumol/min/g X wet wt per mM K+. Lactate release changed markedly but transiently, about 1 min after changing the extracellular K+ concentration, and its amount varied linearly with the K+ concentration. In the steady state, however, lactate release was almost independent of the extracellular K+ concentration, although oxidized pyridine nucleotide increased with increasing K+ concentration. Coronary flow increased with the extracellular K+ concentration. Heart rate changed little between 1 and 12 mM K+, but decreased sharply above 12 mM K+. At 20 mM K+, heart beat was arrested and approximately 40% of myoglobin was deoxygenated. The intracellular oxygen concentration was estimated to be about 10 microM even during aerobic perfusion. Similarly, Ca2+-free arrested heart was found to be in a hypoxic state. The results showed that oxygen entry into cardiac tissue is facilitated by the cardiac cycle.
在无血红蛋白灌注的大鼠心脏上进行的不同灌注压力实验中，发现氧消耗和吡啶核苷酸的氧化还原变化与心脏做功呈线性关系。这种关系被用于分析与离子泵相关的能量代谢。诸如左心室压力和心率等机械活动随细胞外钾离子浓度而变化。以正常（4.7 mM）和其他各种细胞外钾离子浓度下的值之差，并校正因机械做功引起的变化来估算，离子泵依赖性的氧消耗和吡啶核苷酸氧化还原状态的变化与钾离子浓度呈线性关系。氧消耗的斜率约为每毫摩尔钾离子0.1微摩尔/分钟/克湿重。乳酸释放显著但短暂地变化，在改变细胞外钾离子浓度后约1分钟出现，其释放量与钾离子浓度呈线性关系。然而，在稳态下，尽管氧化型吡啶核苷酸随钾离子浓度增加而增加，但乳酸释放几乎与细胞外钾离子浓度无关。冠状动脉血流量随细胞外钾离子浓度增加而增加。心率在1至12 mM钾离子之间变化不大，但在12 mM以上急剧下降。在20 mM钾离子时，心跳停止，约40%的肌红蛋白脱氧。即使在有氧灌注期间，细胞内氧浓度估计约为10 microM。同样，无钙停搏心脏被发现处于缺氧状态。结果表明，心脏周期促进了氧进入心脏组织。
