乳酸刺激下分离的大鼠肝细胞中的乙醇氧化作用。

Lactate-stimulated ethanol oxidation in isolated rat hepatocytes.

作者信息

Crow K E, Cornell N W, Veech R L

出版信息

Biochem J. 1978 Apr 15;172(1):29-36. doi: 10.1042/bj1720029.

DOI:10.1042/bj1720029

PMID:656074

原文链接:https://pmc.ncbi.nlm.nih.gov/articles/PMC1185658/

Abstract

Hepatocytes isolated from starved rats and incubated without other substrates oxidized ethanol at a rate of 0.8-0.9mumol/min per g wet wt. of cells. Addition of 10mm-lactate increased this rate 2-fold. 2. Quinolinate (5mm) or tryptophan (1mm) decreased the rate of gluconeogenesis with 10mm-lactate and 8mm-ethanol from 0.39 to 0.04-0.08mumol/min per g wet wt. of cells, but rates of ethanol oxidation were not decreased. From these results it appears that acceleration of ethanol oxidation by lactate is not dependent upon the stimulation of gluconeogenesis and the consequent increased demand for ATP. 3. As another test of the relationship between ethanol oxidation and gluconeogenesis, the initial lactate concentration was varied from 0.5mm to 10mm and pyruvate was added to give an initial [lactate]/[pyruvate] ratio of 10. This substrate combination gave a large stimulation of ethanol oxidation (from 0.8 to 2.6mumol/min per g wet wt. of cells) at low lactate concentrations (0.5-2.0mm), but rates remained nearly constant (2.6-3.0mumol/min per g wet wt. of cells) at higher lactate concentrations (2.0-10mm). 4. In contrast, owing to the presence of ethanol, the rate of glucose synthesis was only slightly increased (from 0.08 to 0.12mumol/min per g wet wt. of cells) between 0.5mm- and 2.0mm-lactate and continued to increase (from 0.12 to 0.65mumol/min per g wet wt. of cells) with lactate concentrations between 2 and 10mm. 5. In the presence of ethanol, O(2) uptake increased with increasing substrate concentration over the entire range. 6. Changes in concentrations of glutamate and 2-oxoglutarate closely paralleled changes in the rate of ethanol oxidation. 7. In isolated hepatocytes, rates of ethanol oxidation are lower than those in vivo apparently because of depletion of malate-aspartate shuttle intermediates during cell preparation. Rates are returned to those observed in vivo by substrates that increase the intracellular concentration of shuttle metabolites.

摘要

从饥饿大鼠分离得到的肝细胞，在无其他底物的情况下孵育时，乙醇氧化速率为每克细胞湿重0.8 - 0.9微摩尔/分钟。添加10毫摩尔/升乳酸后，该速率增加了2倍。2. 喹啉酸（5毫摩尔/升）或色氨酸（1毫摩尔/升）使利用10毫摩尔/升乳酸和8毫摩尔/升乙醇进行糖异生的速率从每克细胞湿重0.39微摩尔/分钟降至0.04 - 0.08微摩尔/分钟，但乙醇氧化速率并未降低。从这些结果看来，乳酸对乙醇氧化的加速作用并不依赖于糖异生的刺激以及随之而来对ATP需求的增加。3. 作为对乙醇氧化与糖异生之间关系的另一项测试，初始乳酸浓度从0.5毫摩尔/升变化至10毫摩尔/升，并添加丙酮酸以使初始[乳酸]/[丙酮酸]比值为10。这种底物组合在低乳酸浓度（0.5 - 2.0毫摩尔/升）时对乙醇氧化有很大刺激作用（从每克细胞湿重0.8微摩尔/分钟增至2.6微摩尔/分钟），但在较高乳酸浓度（2.0 - 10毫摩尔/升）时速率几乎保持恒定（每克细胞湿重2.6 - 3.0微摩尔/分钟）。4. 相比之下，由于乙醇的存在，在0.5毫摩尔/升至2.0毫摩尔/升乳酸之间，葡萄糖合成速率仅略有增加（从每克细胞湿重0.08微摩尔/分钟增至0.12微摩尔/分钟），而在乳酸浓度为2至10毫摩尔/升时继续增加（从每克细胞湿重0.12微摩尔/分钟增至0.65微摩尔/分钟）。5. 在有乙醇存在的情况下，整个底物浓度范围内氧气摄取量随底物浓度增加而增加。6. 谷氨酸和2 - 氧代戊二酸浓度的变化与乙醇氧化速率的变化密切平行。7. 在分离的肝细胞中，乙醇氧化速率低于体内的速率，显然是因为细胞制备过程中苹果酸 - 天冬氨酸穿梭中间体的消耗。通过增加穿梭代谢物细胞内浓度的底物，速率可恢复到体内观察到的水平。