RESPONSE OF FETAL-RAT LUNG FIBROBLASTS TO ELEVATED OXYGEN CONCENTRATIONS AFTER LIPOSOME-MEDIATED AUGMENTATION OF ANTIOXIDANT ENZYMES

Cultured fetal rat lung fibroblasts are growth-inhibited and have increased lactate dehydrogenase release and prosta glandin synthesis in response to 50% and 95% oxygen exposure. Extended exposure to 50% oxygen, but not to 95% oxygen, was associated with tolerance to the cytotoxic effects of oxygen. Pretreatment of fibroblasts with liposome-encapsulated superoxide dismutase and catalase also conferred protection against the cytotoxic effects of 50% and 95% oxygen. Exogenous enhancement of intracellular superoxide dismutase and catalase specific activities did not attenuate the growth inhibition or increased prostaglandin synthesis associated with exposure to 50% or 95% oxygen. The growth inhibition could not be attributed to an automne prostaglandin effect, since inhibition of prostaglandin synthesis with 50 μM ibuprofen did not prevent O2-mediated inhibition of DNA synthesis. © 1990.