Glutathione redox status of control and cadmium oxide-exposed rat lungs during oxidant stress

Activities of enzymes responsible for the maintenance of reduced glutathione (GSH) levels have been shown in a previous study to be increased in rat lungs following a 3-h exposure to cadmium oxide aerosols at 5.0 mg/m3. In this study, the ability of the lung to maintain levels of GSH during challenge with tert-butyl hydroperoxide (tBuOOH) was evaluated in isolated perfused lungs from control and cadmium oxide-exposed rats. Changes in glutathione redox status were indicated by measurements of nonprotein sulfhydryls (NPSH), total glutathione (1/2 GSH + GSSG), and glutathione disulfide (GSSG) in liquid nitrogen freeze-clamped lungs after 3-min infusions with 0-0.6 mM tBuOOH. In control and cadmium oxide-exposed lungs, levels of 1/2 GSH + GSSG remained constant over the range of 0-0.6 mM tBuOOH, indicating that no loss of glutathione from the system had occurred. In experiments with control lungs, levels of NPSH fell from 8.04 +/- 0.22 to 3.09 +/- 0.40 mumol/g dry weight when tBuOOH concentrations were increased from 0 to 0.6 mM (n = 20-23). In cadmium oxide-exposed lungs, NPSH levels also decreased proportionally to increases in GSSG. However, at concentrations of 0.075 and 0.15 mM tBuOOH, significantly smaller decreases in NPSH levels were observed in cadmium oxide-exposed lungs compared with controls. This protection against the GSH-depleting effects of tBuOOH might be explained by increased tissue levels of GSH-related enzymes.