REDOX STATE OF FREE NICOTINAMIDE-ADENINE DINUCLEOTIDE IN CYTOPLASM AND MITOCHONDRIA OF RAT LIVER
REDOX STATE OF FREE NICOTINAMIDE-ADENINE DINUCLEOTIDE IN CYTOPLASM AND MITOCHONDRIA OF RAT LIVER
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DOI：
10.1042/bj1030514
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发表时间：
1967-01-01
影响因子：
4.1
通讯作者：
KREBS, HA
中科院分区：
文献类型：
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作者：
WILLIAMSON, DH;LUND, P;KREBS, HA
在死亡后尽快在冷冻夹闭的大鼠肝脏中测量乳酸-、[β] -羟基丁酸-和谷氨酸-脱氢酶系统的氧化和还原底物的浓度。这些脱氢酶的底物可能与游离NAD+和NADH平衡，并且游离二核苷酸的比率可以从底物的测量浓度和平衡常数计算（Holzer，Schultz和Lynen，1956; Biicher和Klingenberg，1958）。乳酸脱氢酶系统反映细胞质中[NAD+]/[NADH]的比值，β-羟丁酸脱氢酶系统反映线粒体嵴中的比值，谷氨酸脱氢酶系统反映线粒体基质中的比值。平衡常数[E.C.]乳酸脱氢酶（EC 1.1.1.27）、[β]-羟基丁酸脱氢酶（EC 1.1.1.30）和苹果酸脱氢酶（EC 1.1.1.37）在接近生理条件下重新测定（38[度]; 10.25）。大鼠肝细胞胞浆[NAD+]/[NADH]的平均值在营养良好的大鼠中为725（9pH7.0），在饥饿的大鼠中为528，在四氧嘧啶糖尿病大鼠中为208。线粒体基质和嵴的[NAD+]/[NADH]比率在相同的代谢状态下给出了几乎相同的值。这表明[β] -羟基丁酸脱氢酶和谷氨酸脱氢酶共享一个共同的二核苷酸库。营养良好的大鼠肝脏线粒体内的平均[NAD+]/[NADH]比值约为8。饥饿时下降到5，四氧嘧啶糖尿病患者上升到10。因此，细胞质和线粒体的[NAD+]/[NADH]比率差异很大，并且当肝脏的代谢状态改变时，不一定平行移动。游离二核苷酸的比率与总二核苷酸的比率有很大差异，因为蛋白质结合的NADH比NAD+多得多。本文讨论了这些发现对各种问题的意义，包括：肝细胞中NAD+[长破折号]NADH池的数量;该方法对肝以外组织的适用性;谷氨酸脱氢酶的转氢酶活性;线粒体和细胞质氧化还原状态差异的生理意义;细胞室氧化还原状态的调节方面;线粒体草酰乙酸的稳态浓度;细胞室的氧化还原状态与酮症之间的关系。
The concentrations of the oxidized and reduced substrates of the iactate-, [beta] -hydroxybutyrate- and glutamate-dehydrogenase systems were measured in rat livers freeze-clamped as soon as possible after death. The substrates of these dehydrogenases are likely to be in equilibrium with free NAD+ and NADH, and the ratio of the free dinucleotides can be calculated from the measured concentrations of the substrates and the equilibrium constants (Holzer, Schultz and Lynen, 1956; Biicher and Klingenberg, 1958). The Iactate-dehydro-genase system reflects the [NAD+]/[NADH] ratio in the cytoplasm, the [beta]-hydroxybutyrate dehydrogenase that in the mitochondrial cristae and the glutamate dehydrogenase that in the mitochondrial matrix. The equilibrium constants [E.C.] of Iactate dehydrogenase (EC 1.1.1.27), [beta]-hydroxybutyrate dehydrogenase (EC 1.1.1.30) and malate dehydrogenase (EC 1.1.1.37) were redetermined for near-physiological conditions (38[degree]; 10.25). The mean [NAD+]/[NADH] ratio of rat-liver cytoplasm was calculated as 725 9pH 7.0) in well-fed rats, 528 in starved rats and 208 in alloxan-diabetic rats. The [NAD+]/[NADH] ratio for the mitochondrial matrix and cristae gave virtually identical values in the same metabolic state. This indicates that [beta] -hydroxybutyrate dehydrogenase and glutamate dehydrogenase share a common pool of dinucleotide. The mean [NAD+]/[NADH] ratio within the liver mitochondria of well-fed rats was about 8. It fell to about 5 in starvation and rose to about 10 in alloxan-diabetes. The [NAD+]/[NADH] ratios of cytoplasm and mitochondria are thus greatly different and do not necessarily move in parallel when the metabolic state of the liver changes. The ratios found for the free dinucleotides differ greatly from those recorded for the total dinucleotides because much more NADH than NAD+ is protein-bound. The bearing of these findings on various problems, including the following, is discussed: the number of NAD+[long dash]NADH pools in liver cells; the applicability of the method to tissues other than liver; the transhydro-genase activity of glutamate dehydrogenase; the physiological significance of the difference of the redox states of mitochondria and cytoplasm; aspects of the regulation of the redox state of cell compartments; the steady-state concentration of mitochondrial oxaloacetate; the relations between the redox state of cell compartments and ketosis.