Glycine protects against hepatocyte killing by KCN or hypoxia by preventing intracellular Na+ overload in the rat.
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.
Carini
R
R
Department of Medical Sciences, University of Torino, Novara, Italy.
Bellomo
G
G
Grazia De Cesaris
M
M
Albano
E
E
D000818:Animals; D002034:Bumetanide / Q000494:pharmacology; D015687:Cell Hypoxia / Q000187:drug effects*; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D002713:Chlorine / Q000032:analysis / Q000502:physiology; D005998:Glycine / Q000494:pharmacology*; D008099:Liver / Q000187:drug effects*; D008297:Male; D008985:Monensin / Q000494:pharmacology; D009579:Nitrobenzoates / Q000494:pharmacology; D011190:Potassium Cyanide / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000032:analysis*; D013331:Strychnine / Q000494:pharmacology
D009579:Nitrobenzoates; D002034:Bumetanide; C058176:5-nitro-2-(3-phenylpropylamino)benzoic acid; D002713:Chlorine; D008985:Monensin; D012964:Sodium; D013331:Strychnine; D011190:Potassium Cyanide; D005998:Glycine