Effect of 60 Hz magnetic field exposure on c-fos expression in stimulated PC12 cells

Rat pheochromocytoma PC12 cells have been treated with nerve growth factor (NGF) at final concentrations of 2, 4, 8, and 16 ng/ml, and then were expos ed to 60-Hz, sinusoidal magnetic fields (MF) of 12.5, 25, 50, and 100 mu T (rms) for 30 min. Transcript levels for both c-fos and glyceraldehyde-3 -ph osphate dehydrogenase were determined by Northern blot analysis using P-32- labeled cDNA probes. No change in c-fos expression was measured at any cond ition employed. Treatment of PC12 cells with a combination of agents (NGF, forskolin, and tetradecanoylphorbol acetate [TPA]) increased c-fos expressi on over that detected with NGF alone. MF exposure of cells treated with the three-agent regimen produced two outcomes, either no change or a doubling of c-fos expression. In subsequent experiments, cells were treated with NGF , NGF + forskolin + TPA, or pre-treated with anisomycin and then treated wi th NGF + forskolin + TPA. It was determined that MF exposure, like superind uction with anisomycin, increased c-fos expression only in cultures which w ere not yet exhibiting maximal c-fos expression. It is hypothesized that MF exposure, like anisomycin, may alter the activity of key intracellular pro tein kinases.