In vitro modulation of antioxidant enzymes in normal and malignant renal epithelium

The activities of three antioxidant enzymes, superoxide dismutase, catalase, and glutathione peroxidase, were monitored in isolated human renal adenocarcinoma tissues and in cultured human renal adenocarcinoma cells. The results were compared to the activities of these enzymes in the proposed cell of origin, isolated human proximal tubular tissues, and cultured proximal tubular epithelial cells. Strong modulation of these enzymes by culture conditions was observed in normal cells but not in carcinoma cells. Low levels of cellular lipid peroxidation, as assessed by levels of malondialdehyde (MDA), were observed in adenocarcinoma cells under the culture conditions tested with one exception: greatly elevated MDA was observed in renal adenocarcinoma cells grown on plastic in serum-free, chemically defined medium. This increased lipid peroxidation correlated with a loss of cell viability under these conditions.