Antioxidant enzymes located in the bronchial epithelium can be expected to be important in protecting these cells against both endogenous and exogenous oxidants. In this study, human bronchial epithelial cells were isolated and cultured from specimens obtained from donors for lung transplantation. The levels and relative importance of different antioxidant enzymes were also assessed using an immortalized human bronchial epithelial cell line (BEAS 2B cells). Immunocytochemical studies showed a similar pattern of intracellular localization with the moderate degrees of labeling for Mn superoxide dismutase (SOD), CuZn SOD, and catalase in freshly isolated bronchial epithelial cells, bronchial epithelial cells in primary culture, and BEAS 2B cells. CuZn SOD and catalase decreased in labeling density whereas Mn SOD was unchanged when bronchial epithelial cells were placed in primary cultures. In contrast, Mn SOD and catalase were decreased in BEAS 2B cells compared with primary cultures. Although Mn SOD was low in BEAS 2B cells, it could be significantly induced by tumor necrosis factor treatment. Biochemical analysis showed remarkably similar catalase and glutathione reductase activities in primary cultured epithelial cells and BEAS 2B cells.(ABSTRACT TRUNCATED AT 250 WORDS)