PO2-dexamethasone interactions in fibroblast growth and antioxidant enzyme activity

Fetal rat lung fibroblasts were cultured in a gas phase of 20% O2, 5% CO2 (PO2 measured, 150 Torr) or 2% oxygen, 5% CO2 (PO2 measured, 25 Torr) with or without 100 nM dexamethasone (Dex). Superoxide dismutase (SOD) activity per cell increased spontaneously during 4 days of incubation at both PO2, but catalase (CAT) activity tended to fall during this time and glutathione peroxidase (GPx) activity showed no consistent trend during this interval. Cells cultured at a low PO2 had a lower protein content and SOD activity compared with air controls. Dex inhibited cell proliferation and enhanced intracellular accumulation of protein at the low PO2 but prevented the increase in protein content without affecting cell multiplication at a PO2 of 150 Torr. SOD activity per cell was enhanced by Dex at a low PO2 but reduced in 20% O2, 5% CO2. An increase in CAT and GPx activity per cell resulted on exposing fibroblasts to Dex in the presence of low PO2. These results show that Dex affects the growth and antioxidant enzyme activity of fetal lung fibroblasts, and this action of Dex can be modulated by changing the ambient PO2.