The alveolar epithelial cells of the lower respiratory tract are exposed continuously to injurious agents, including oxygen radicals. The type II alveolar epithelial cell is critically important to the normal function of the lung, because it is responsible for synthesis of surfactant and other essential duties. In the current investigation, the authors documented the loss of intracellular adenosine triphosphate (ATP) after exposure of the cells to sublethal concentrations of hydrogen peroxide (H2O2) and hypochlorous acid. Subsequent experiments attempted to alleviate or prevent this oxidant mediated loss of ATP by preincubating the cells with either glutathione or N-acetylcysteine (NAC). Initially, it was determined that exposure of the type II cells to 250 microM hypochlorous acid or 250 microM H2O2 for 1 hour each would cause significant loss of type II cell ATP. However, preincubation with glutathione (1,000 microM) inhibited the loss of ATP after both exposure to 250 microM H2O2 (24 +/- 3% loss of ATP without glutathione compared with 13 +/- 2% loss with glutathione, P < 0.05), and 250 microM hypochlorous acid (12 +/- 2% loss of ATP without glutathione compared with 1 +/- 1% increase of ATP with glutathione). Similar results were obtained using NAC (2 mg/mL) after exposure to 250 microM H2O2 (23 +/- 2% loss of ATP without NAC compared with a 4 +/- 3% loss of ATP with NAC). This study demonstrates that exogenous glutathione and NAC are able to protect type II cells from oxidant mediated sublethal injury and loss of intracellular ATP stores.