Carini R, Bellomo G, Grazia De Cesaris M, Albano E
Department of Medical Sciences, University of Torino, Novara, Italy.
Hepatology. 1997 Jul;26(1):107-12. doi: 10.1002/hep.510260114.
Glycine has been shown to prevent hepatocyte death induced by anoxia and by several toxic agents. However, the mechanisms responsible for such a cytoprotective effect have not yet been entirely clarified. We have previously shown that an uncontrolled increase in intracellular Na+ is critical for hepatocyte killing induced by adenosine triphosphate (ATP) depletion. We herein report that protection by glycine (2 mmol/L) against cytotoxicity induced in isolated rat hepatocyte by potassium cyanide (KCN) or hypoxia was associated with the prevention of cytosolic Na+ accumulation. The addition of the Na+ ionophore, monensin, abolished the effects of glycine on both Na+ increase and cytotoxicity. Pretreating hepatocytes with the glycine-receptor antagonist, strychnine (1 mmol/L), similarly prevented Na+ overload and cell killing. Glycine at high concentrations and strychnine are known to block Cl- channels in many cell types. Consistently, we have observed that glycine and strychnine prevented the increase of intracellular Cl- levels caused by hypoxia or KCN. Incubation of hepatocytes in a Cl(-)-free medium, obtained by substituting chloride with membrane-impermeable gluconate, significantly reduced Na+ accumulation and cell killing triggered by hypoxia or KCN. Both these effects were abolished by the addition of monensin. The cytoprotective action exerted by hepatocyte incubation in the Cl(-)-free medium was, however, lost when membrane-permeable nitrate, which allowed Na+ accumulation, was used instead to replace chloride. Altogether, these results indicate that glycine inhibition of Cl- conductance protects against hepatocyte killing induced by KCN and hypoxia by interfering with intracellular Na+ accumulation triggered by ATP depletion.
甘氨酸已被证明可预防缺氧和多种毒性剂诱导的肝细胞死亡。然而，这种细胞保护作用的机制尚未完全阐明。我们之前已经表明，细胞内钠离子（Na⁺）不受控制的增加对于三磷酸腺苷（ATP）耗竭诱导的肝细胞杀伤至关重要。我们在此报告，甘氨酸（2 mmol/L）对氰化钾（KCN）或缺氧诱导的离体大鼠肝细胞细胞毒性的保护作用与防止细胞质Na⁺积累有关。添加Na⁺离子载体莫能菌素消除了甘氨酸对Na⁺增加和细胞毒性的影响。用甘氨酸受体拮抗剂士的宁（1 mmol/L）预处理肝细胞同样可防止Na⁺过载和细胞死亡。已知高浓度的甘氨酸和士的宁可阻断许多细胞类型中的氯离子（Cl⁻）通道。一致地，我们观察到甘氨酸和士的宁可防止缺氧或KCN引起的细胞内Cl⁻水平升高。通过用膜不可渗透的葡萄糖酸盐替代氯离子获得的无Cl⁻培养基中培养肝细胞，可显著减少缺氧或KCN引发的Na⁺积累和细胞死亡。添加莫能菌素可消除这两种作用。然而，当使用允许Na⁺积累的膜可渗透硝酸盐替代氯离子时，在无Cl⁻培养基中培养肝细胞所发挥的细胞保护作用丧失。总之，这些结果表明，甘氨酸对Cl⁻电导的抑制作用通过干扰ATP耗竭引发的细胞内Na⁺积累，从而保护肝细胞免受KCN和缺氧诱导的细胞死亡。
