A CRITICAL ROLE FOR THIOL, BUT NOT ATP, DEPLETION IN 95-PERCENT O-2-MEDIATED INJURY OF PRETERM PNEUMOCYTES IN-VITRO

Prolonged exposure to elevated partial pressures of oxygen results in lung cell toxicity, both in vivo and in vitro, due to the excess produ ction and target molecule reactions of reactive oxygen species. Events primarily responsible for cell death vary with the type of oxidant in jury and with cell type. Because of the susceptibility of the prematur e lung to oxygen toxicity, and the critical barrier function of the ep ithelium, we have investigated the role of two potentially lethal cons equences of O-2 exposure in premature distal lung epithelial cells in vitro. A 48-h exposure of distal fetal rat lung epithelial cells to 95 % O-2 caused cytotoxicity, which was associated with DNA injury and de pletion of both cellular protein and nonprotein reduced sulfhydryls. T he observed DNA injury preceded other markers of cell injury and was n ot sufficient to either activate the chromosomal enzyme poly(ADP-ribos e) polymerase or cause secondary ATP depletion. Buthionine sulfoxamine -induced depletion of nonprotein reduced sulfhydryls increased the sen sitivity of cells to subsequent O-2-mediated cytotoxicity. Addition of the glutathione precursor N-acetylcysteine to the culture medium main tained cellular protein and nonprotein reduced sulfhydryl concentratio ns and prevented O-2-mediated cytotoxicity. We conclude that loss of p rotein and nonprotein reduced sulfhydryls, but not DNA injury, is caus ally related to the toxic effects of elevated O-2 on premature distal lung epithelial cells. (C) 1994 Academic Press, Inc.