Carini R, Bellomo G, Benedetti A, Fulceri R, Gamberucci A, Parola M, Dianzani M U, Albano E
Department of Experimental Medicine and Oncology, University of Torino, Italy.
Hepatology. 1995 Apr;21(4):1089-98.
The exposure of isolated hepatocytes to the redox-cycling quinone menadione caused an early loss of mitochondrial membrane potential, adenosine triphosphate (ATP) depletion, and decreased intracellular pH. These alterations were followed by an increase in intracellular Na+ and, ultimately, cell death. If HCO3- was omitted from the incubation buffer, or the hepatocytes were incubated in an acidic medium (pH 6.5) the accumulation of Na+ was markedly reduced. Inhibition of the Na+/H+ exchanger and of the Na+/HCO3- cotransporter by, respectively, amiloride and 4,4'-di-isothiocyano-2,2'-disulfonic acid stilbene (DIDS) suppressed the initial Na+ influx but did not prevent subsequent Na+ accumulation, because amiloride and DIDS inhibited the Na+/K+ pump. The omission of HCO3- from the extracellular medium or the incubation in acidic conditions also prevented menadione toxicity, without interfering with the loss of mitochondrial membrane potential and with ATP depletion. A similar protection was evident when hepatocytes were incubated with menadione in a medium without Na+. The preservation of adequate levels of ATP by supplementing hepatocytes with fructose allowed the initial Na+ load to be recovered and provided partial protection against menadione toxicity. These effects were suppressed if Na+/K(+)-ATPase was inhibited with ouabain. Taken together, these results indicated that the activation of the Na+/HCO3- cotransporter and of the Na+/H+ exchanger in response to the decrease of intracellular pH stimulated an enhanced influx of Na+. When the activity of the Na+/K+ pump was not able to control Na+ levels because of ATP depletion, such an uncontrolled Na+ influx precipitated irreversible injury and caused hepatocyte death.
将分离的肝细胞暴露于氧化还原循环醌维生素K3会导致线粒体膜电位早期丧失、三磷酸腺苷（ATP）耗竭以及细胞内pH值降低。这些改变之后是细胞内钠离子增加，最终导致细胞死亡。如果在孵育缓冲液中省略碳酸氢根离子（HCO3-），或者将肝细胞在酸性培养基（pH 6.5）中孵育，钠离子的积累会显著减少。分别用氨氯吡咪和4,4'-二异硫氰酸-2,2'-二磺酸芪（DIDS）抑制钠离子/氢离子交换体和钠离子/碳酸氢根共转运体，可抑制最初的钠离子内流，但不能阻止随后的钠离子积累，因为氨氯吡咪和DIDS抑制了钠钾泵。从细胞外培养基中省略HCO3-或在酸性条件下孵育也可防止维生素K3的毒性，而不干扰线粒体膜电位的丧失和ATP的耗竭。当肝细胞在无钠离子的培养基中与维生素K3一起孵育时，也有类似的保护作用。通过向肝细胞补充果糖来维持足够水平的ATP，可使最初的钠离子负荷恢复，并提供部分抗维生素K3毒性的保护作用。如果用哇巴因抑制钠钾ATP酶，这些作用就会受到抑制。综上所述，这些结果表明，细胞内pH值降低时，钠离子/碳酸氢根共转运体和钠离子/氢离子交换体的激活会刺激钠离子内流增加。当由于ATP耗竭，钠钾泵的活性无法控制钠离子水平时，这种不受控制的钠离子内流会导致不可逆损伤并引起肝细胞死亡。
