McCall D, Henderson G I, Gray P, Schenker S
Department of Medicine, University of Texas Health Science Center, San Antonio 78284.
Biochem Pharmacol. 1989 Aug 15;38(16):2593-600. doi: 10.1016/0006-2952(89)90543-1.
To define further the influence of ethanol on membranes, its effects on Na+ pump function were studied in monolayer cultures of fetal rat hepatocytes. The effects of ethanol (2 and 4 mg/ml) on total K+ influx, ouabain-sensitive K+ influx, Na+ pump density (from specific [3H]ouabain binding), pump turnover rates and intracellular Na+ were measured following exposure of the cells to ethanol for 1-24 hr. In parallel studies, the effects of ethanol (2 mg/ml) on cell water content and membrane fluidity were measured. Ethanol had no immediate effect on K+ influx, but after 1 hr ethanol in concentrations of 2 and 4 mg/ml decreased the total K+ influx (mumol/10(11) cells/sec) from a control of 8.5 +/- 0.64 to 4.46 +/- 0.50 and 4.09 +/- 0.26 respectively (N = 6 for each experiment; P less than 0.001). This represented the maximum effect of ethanol since after 6 and 24 hr of ethanol treatment the K+ influx had increased towards control levels but remained significantly (P less than 0.01 for 2 mg/ml and P less than 0.001 for 4 mg/ml) below that in control cells even at 24 hr. The decrease in K+ influx reflected a decrease in mean ouabain-sensitive K+ influx from a control of 5.87 to 3.24 and 2.70 (mumol/10(11) cells/sec) after a 1-hr treatment with 2 and 4 mg ethanol/ml medium respectively. Ethanol (2 mg/ml) treatment for 1-hr decreased Na+ pump density (x 10(5) molecules ouabain per cell) from a control of 2.80 +/- 0.30 to 1.70 +/- 0.11 (P less than 0.001). At 6 and 24 hr [3H]ouabain binding showed a pattern similar to that seen with the K+ influx, tending to return to pretreatment levels. There was no change in individual pump turnover rates in the presence of ethanol. Following exposure to ethanol, cellular Na+ content steadily increased over the first 6 hr and then returned to control levels. When corrected for parallel changes in cell volume, however, intracellular Na+ concentration increased by 17% (P less than 0.01) after 1 hr and thereafter remained at this higher level throughout the 24-hr period. Measurements of membrane fluidity showed that it was increased markedly by ethanol at a concentration of 2 mg/ml and that the effect bore a close temporal relationship to the changes in active K+ influx and Na+ pump density. We conclude that ethanol has a depressant effect on hepatic Na+ pump function, resulting in an increase in intracellular Na+ and an eventual gain in cell water.(ABSTRACT TRUNCATED AT 400 WORDS)
为了进一步明确乙醇对细胞膜的影响，我们在胎鼠肝细胞单层培养物中研究了乙醇对钠泵功能的作用。在细胞暴露于乙醇1 - 24小时后，测定了乙醇（2和4毫克/毫升）对总钾离子内流、哇巴因敏感的钾离子内流、钠泵密度（通过特异性[3H]哇巴因结合测定）、泵周转率以及细胞内钠离子的影响。在平行研究中，测定了乙醇（2毫克/毫升）对细胞含水量和膜流动性的影响。乙醇对钾离子内流没有即时作用，但1小时后，浓度为2和4毫克/毫升的乙醇使总钾离子内流（微摩尔/10^11个细胞/秒）分别从对照值8.5±0.64降至4.46±0.50和4.09±0.26（每个实验N = 6；P < 0.001）。这代表了乙醇的最大作用，因为乙醇处理6小时和24小时后，钾离子内流已向对照水平增加，但即使在24小时时仍显著低于对照细胞（2毫克/毫升时P < 0.01，4毫克/毫升时P < 0.001）。钾离子内流的减少反映了平均哇巴因敏感的钾离子内流从对照值5.87分别降至用2毫克/毫升乙醇/培养基处理1小时后的3.24和4毫克/毫升乙醇处理1小时后的2.70（微摩尔/10^11个细胞/秒）。用2毫克/毫升乙醇处理1小时使钠泵密度（每个细胞哇巴因分子×10^5）从对照值2.80±0.30降至1.70±0.11（P < 0.001）。在6小时和24小时时，[3H]哇巴因结合呈现出与钾离子内流相似的模式，趋于恢复到预处理水平。在有乙醇存在的情况下，单个泵的周转率没有变化。暴露于乙醇后，细胞内钠离子含量在最初6小时内稳步增加，然后恢复到对照水平。然而，校正细胞体积的平行变化后，细胞内钠离子浓度在1小时后增加了17%（P < 0.01），并在整个24小时期间保持在较高水平。膜流动性测量表明，浓度为2毫克/毫升的乙醇显著增加了膜流动性，且这种作用与主动钾离子内流和钠泵密度的变化具有密切的时间关系。我们得出结论，乙醇对肝脏钠泵功能有抑制作用，导致细胞内钠离子增加并最终使细胞含水量增加。（摘要截断于400字）
