Alterations of Na+ homeostasis in hepatocyte reoxygenation injury

Reperfusion injury represents an important cause of primary graft non-funct ion during liver transplantation. However, the mechanism responsible for ce llular damage during reoxygenation has not yet been completely understood. We have investigated whether changes in intracellular Na+ distribution migh t contribute to cause hepatocyte damage during reoxygenation buffer after 2 4 h of cold storage. Hepatocyte reoxygenation resulted in a rapid increase in cellular Na+ content that was associated with cytotoxicity. Na+ accumula tion and hepatocyte death were prevented by the omission of Na+ from the in cubation medium, but not by the addition of antioxidants. Blocking Na+/H+ e xchanger and Na+/HCO3- cotransporter by, respectively, 5-(N,N-dimethyl)-ami loride or omitting HCO3- from the reoxygenation medium significantly decrea sed Na+ overload and cytotoxicity. Stimulation of ATP re-synthesis by the a ddition of fructose also lowered Na+ accumulation and cell death during reo xygenation. A significant protection against Na+-mediated reoxygenation inj ury was evident in hepatocytes maintained in an acidic buffer (pH 6.5) or i n the presence of glycine. The cytoprotective action of glycine or of the a cidic buffer was reverted by promoting Na+ influx with the Na+/H+ ionophore monensin. Altogether, these results suggest that Na+ accumulation during t he early phases of reoxygenation might contribute to liver graft reperfusio n injury. (C) 2000 Elsevier Science B.V. All rights reserved.