The involvement of hydroxyl free radicals in differentiation of the PC-12 rat pheochromocytoma cell line

These experiments tested the differentiation properties of the PC-12 cell line under conditions of in vitro generation of OH free radicals by Fenton reaction. This involves the simultaneous addition of the following reactants: ADP–Fe2+-complex (0.1 mM for iron) and H2O2 (0.025 mM), final concentrations. Superoxide dismutase activity, the increase of which is considered as a marker of differentiation, catalase and glutathione peroxidase enzyme activities were investigated, which all displayed significant increases after single and repeated interventions with hydroxyl free radicals, while the cell number remained nearly at the starting-value. It is known that the differentiation takes place when the cell number has reached a plateau. These data, therefore, suggest that hydroxyl free radicals can induce in vitro cell differentiation, and that they play a more complex role in cell physiology than simply causing oxidative damages. It is interesting that the cells can maintain high levels of these enzyme activities for a relatively long time (2 or 4 days) after a very short flux of hydroxyl free radicals.