Pascale R, Daino L, Garcea R, Frassetto S, Ruggiu M E, Vannini M G, Cozzolino P, Feo F
Istituto di Patologia generale dell'Università di Sassari, Italy.
Toxicol Appl Pharmacol. 1989 Feb;97(2):216-29. doi: 10.1016/0041-008x(89)90327-x.
(Na+,K+)ATPase activity of rat liver plasma membranes was evaluated in female rats feeding an ethanol containing diet for 46 days (total ethanol ingested, 59.7 g/100 g body wt). Determinations were performed at the end of ethanol treatment or at various times after stopping treatment. (Na+,K+)ATPase and 5'-nucleotidase activities exhibited a 8- and 1.4-fold decrease, respectively, at the end of ethanol ingestion. In contrast no modifications of Mg2+-ATPase activity were observed. There also occurred, in ethanol-treated rats, release of sorbitol dehydrogenase into the blood, fat accumulation in liver cells, and decrease in reduced glutathione (GSH) liver content. A decrease in (Na+,K+)ATPase activity was also found in plasma membranes isolated from hepatocyte suspensions after a 2-hr incubation with 50 mM ethanol or 1 mM acetaldehyde (ACA), in conditions that caused a great fall in hepatocyte GSH content but did not cause cell death. After the cessation of ethanol administration, there occurred a progressive recovery of (Na+,K+)ATPase activity, GSH and triacylglycerol content, and release of sorbitol dehydrogenase. These parameters reached control values 12 hr after ethanol withdrawal. S-Adenosyl-L-methionine (SAM), L-methionine, and N-acetylcysteine (NAC), given to rats during ethanol treatment, prevented the decrease in (Na+,K+)ATPase activity and GSH content. They also reduced steatosis and liver necrosis. The efficiency of these compounds decreased in this order: SAM, methionine, NAC. SAM accelerated the recovery of all parameters studied after ethanol withdrawal, and also protected (Na+,K+)ATPase activity and GSH content of isolated hepatocytes from the deleterious effect of ethanol. These SAM effects were prevented by 1-chloro-2,4-dinitro-benzene, a compound which depletes cell GSH. Treatment of isolated hepatocytes with [35S]SAM led to the synthesis of labeled GSH. The total amount and specific activity of labeled GSH underwent a significant increase, in the presence of 2 mM ethanol or 0.5 mM ACA, which indicates a marked stimulation of GSH synthesis by ethanol and ACA. These data indicate that ethanol intoxication may inhibit (Na+,K+)ATPase activity; an effect that does not seem to depend on cell necrosis. SAM, methionine, and NAC exert various degrees of protection toward ethanol-induced cell injury, which are related to the efficiency of these compounds in maintaining a high GSH pool.
在喂食含乙醇饮食46天（总乙醇摄入量为59.7 g/100 g体重）的雌性大鼠中，评估了大鼠肝脏质膜的(Na +,K +)ATP酶活性。在乙醇处理结束时或停止处理后的不同时间进行测定。在乙醇摄入结束时，(Na +,K +)ATP酶和5'-核苷酸酶活性分别下降了8倍和1.4倍。相比之下，未观察到Mg2 + -ATP酶活性的改变。在乙醇处理的大鼠中，还出现了山梨醇脱氢酶释放到血液中、肝细胞脂肪堆积以及肝脏中还原型谷胱甘肽（GSH）含量降低的情况。在用50 mM乙醇或1 mM乙醛（ACA）孵育2小时后，从肝细胞悬液中分离的质膜中也发现(Na +,K +)ATP酶活性降低，在这种情况下肝细胞GSH含量大幅下降，但未导致细胞死亡。停止给予乙醇后，(Na +,K +)ATP酶活性、GSH和三酰甘油含量以及山梨醇脱氢酶的释放出现了逐渐恢复。这些参数在乙醇戒断后12小时达到对照值。在乙醇处理期间给予大鼠S-腺苷-L-甲硫氨酸（SAM）、L-甲硫氨酸和N-乙酰半胱氨酸（NAC），可防止(Na +,K +)ATP酶活性和GSH含量降低。它们还减少了脂肪变性和肝坏死。这些化合物的效果按以下顺序降低：SAM、甲硫氨酸、NAC。SAM加速了乙醇戒断后所研究的所有参数的恢复，还保护分离的肝细胞的(Na +,K +)ATP酶活性和GSH含量免受乙醇的有害影响。1-氯-2,4-二硝基苯可防止这些SAM效应，该化合物会耗尽细胞内的GSH。用[35S]SAM处理分离的肝细胞可导致标记GSH的合成。在存在2 mM乙醇或0.5 mM ACA的情况下，标记GSH的总量和比活性显著增加，这表明乙醇和ACA对GSH合成有明显刺激作用。这些数据表明乙醇中毒可能会抑制(Na +,K +)ATP酶活性；这种效应似乎不依赖于细胞坏死。SAM、甲硫氨酸和NAC对乙醇诱导的细胞损伤具有不同程度的保护作用，这与这些化合物维持高GSH池的效率有关。
