Thurman R G, McKenna W R, Brentzel H J, Hesse S
Fed Proc. 1975 Oct;34(11):2075-81.
Rat liver microsomes oxidized ethanol two to three times faster than propanol when incubated with either an NADPH- or an H2O2-generating system. In addition, solubilized, purified microsomal subfractions were found to contain protein with an electrophoretic mobility identical to rat liver catalase on SDS polyacrylamide gels, suggesting that the separation of catalase from cytochrome P-450 and other microsomal components may not be feasible. These data support the postulate that catalase is responsible for NADPH-dependent microsomal ethanol oxidation. Direct read-out techniques for pyridine nucleotides, the catalase-H2O2 complex, and cytochrome P-450 were utilized to evaluate the specificity of inhibitors of alcohol dehydrogenase (4-methylpyrazole; 4 mM) and catalase (aminotriazole; 1.0 g/kg) qualitatively in perfused rat livers. 4-Methylpyrazole and aminotriazole are specific inhibitors for alcohol dehydrogenase and catalase, respectively, under these conditions. Neither inhibitor nor a combination of them altered the mixed function oxygen of p-nitroanisole to p-nitrophenol as observed by oxygen uptake and product formation. When ethanol utilization was measured over the concentration range 20-80 mM in perfused liver, a concentration dependence was observed. At low concentrations of ethanol, ethanol oxidation was almost totally abolished by 4-methylpyrazole; however, the contribution of 4-methylpyrazole-insensitive ethanol uptake increased as a function of ethanol concentration. At 80 mM ethanol, ethanol utilization was nearly 50% methylpyrazole-insensitive. This portion of ethanol oxidation, however, was abolished by aminotriazole. The data indicate that alcohol dehydrogenase and catalase-H2O2 are responsible for hepatic ethanol oxidation. At low ethanol concentrations (less than 20 mM), alcohol dehydrogenase is predominant; however, at higher ethanol concentrations (up to 80 mM), the contribution of catalase-H2O2 to overall ethanol utilization is significant. No evidence that the endoplasmic reticulum is involved in ethanol metabolism in the perfused liver emerged from these studies.
当与NADPH生成系统或H₂O₂生成系统一起孵育时，大鼠肝脏微粒体氧化乙醇的速度比氧化丙醇的速度快两到三倍。此外，发现溶解并纯化的微粒体亚组分在SDS聚丙烯酰胺凝胶上含有一种电泳迁移率与大鼠肝脏过氧化氢酶相同的蛋白质，这表明将过氧化氢酶与细胞色素P-450及其他微粒体成分分离可能不可行。这些数据支持了过氧化氢酶负责NADPH依赖的微粒体乙醇氧化这一假设。利用针对吡啶核苷酸、过氧化氢酶-H₂O₂复合物和细胞色素P-450的直接检测技术来定性评估灌注大鼠肝脏中乙醇脱氢酶抑制剂（4-甲基吡唑；4 mM）和过氧化氢酶抑制剂（氨基三唑；1.0 g/kg）的特异性。在这些条件下，4-甲基吡唑和氨基三唑分别是乙醇脱氢酶和过氧化氢酶的特异性抑制剂。通过氧气摄取和产物形成观察到，无论是单独的抑制剂还是它们的组合都没有改变对硝基苯甲醚向对硝基苯酚的混合功能氧化。当在灌注肝脏中测量20-80 mM浓度范围内的乙醇利用情况时，观察到了浓度依赖性。在低浓度乙醇时，4-甲基吡唑几乎完全消除了乙醇氧化；然而，对4-甲基吡唑不敏感的乙醇摄取量随着乙醇浓度的增加而增加。在80 mM乙醇时，乙醇利用量近50%对甲基吡唑不敏感。然而，这部分乙醇氧化被氨基三唑消除。数据表明乙醇脱氢酶和过氧化氢酶-H₂O₂负责肝脏乙醇氧化。在低乙醇浓度（低于20 mM）时，乙醇脱氢酶起主要作用；然而，在较高乙醇浓度（高达80 mM）时，过氧化氢酶-H₂O₂对总体乙醇利用的贡献很大。这些研究没有发现内质网参与灌注肝脏中乙醇代谢的证据。
