Pohl K, Letko G, Bohnensack R
Institute of Biochemistry, Medical Academy of Magdeburg, GDR.
Biomed Biochim Acta. 1990;49(1):27-34.
The influence of lactate and ornithine on the mitochondrial redox state as indicated by the 3-hydroxybutyrate/acetoacetate ratio was studied in isolated hepatocytes. The load on the hepatic energy metabolism when lactate and/or ornithine are additionally present can be higher than in the sole presence of octanoic acid. This was revealed by enhanced oxidative turnover rates and higher 3-hydroxybutyrate/acetoacetate ratios at identical rates of respiration. During gluconeogenesis from lactate, such an improved energy supply takes place through more intense oxidation of octanoic acid in the citric-acid cycle. In addition to octanoate oxidation, however, ornithine supplies substrate hydrogen through its catabolism to glutamate as was demonstrated by comparative studies in isolated rat liver mitochondria. The ambivalent character of lactate and ornithine with regard to loading and supplying the energy metabolism seems to substantially account for energetic homoeostasis of the liver.
在分离的肝细胞中研究了乳酸和鸟氨酸对线粒体氧化还原状态（以3-羟基丁酸/乙酰乙酸比率表示）的影响。当额外存在乳酸和/或鸟氨酸时，肝脏能量代谢的负荷可能高于仅存在辛酸时的负荷。这在相同呼吸速率下氧化周转率增强和3-羟基丁酸/乙酰乙酸比率更高的情况下得以体现。在由乳酸进行糖异生的过程中，这种改善的能量供应是通过柠檬酸循环中辛酸更强烈的氧化来实现的。然而，除了辛酸氧化外，鸟氨酸通过其分解代谢为谷氨酸提供底物氢，这在分离的大鼠肝线粒体的比较研究中得到了证实。乳酸和鸟氨酸在能量代谢的负荷和供应方面的矛盾特性似乎在很大程度上解释了肝脏的能量稳态。
