Protection by glycine against hypoxic injury of rat hepatocytes: inhibition of ion fluxes through nonspecific leaks

Background/Aims: Glycine has long been shown to exert strong protective eff ects against hypoxic injury of hepatocytes. Recently, it was suggested that glycine exerts this protection via inhibition of ligand-gated chloride cha nnels, thereby secondarily inhibiting sodium influx. The purpose of this st udy was to examine this suggestion. Methods: Cultured rat hepatocytes were incubated under normoxic and hypoxic conditions. Loss of viability was determined by release of lactate dehydro genase. Cytosolic ion concentrations were measured using digital fluorescen ce microscopy. Results: Glycine prevented the hypoxic increase in cytosolic sodium and str ongly protected against hypoxic injury, The amino acid was not only protect ive in Krebs-Henseleit buffer but also in a chloride-free modification ther eof and offered additional protection in a sodium-fi ee medium (which alrea dy yielded substantial protection in its own right). Glycine also prevented the hypoxic release of the anionic fluorescent dye Newport Green and appea red to prevent the hypoxic entrance of the "'nonphysiological" cations coba lt and nickel. Conclusion: The results strongly argue against inhibition of ligand-gated c hloride channels as being responsible for the potent protective effect of g lycine against hypoxic injury of hepatocytes. Instead, they suggest that gl ycine prevents the formation of nonspecific leaks for small ions including sodium, thereby providing protection.