Exposure to power frequency magnetic fields and X-rays induces GAP-43 gene expression in human glioma MO54 cells

We investigated the distribution and expression of growth associated protein-43 (GAP-43) in human glioma cells (MO54) after exposure to a magnetic field (60 Hz, 5 mT), with or without initial X-ionizing radiation (2 Gy), by using immunocytochemistry and the reverse transcription polymerase chain reaction (RT-PCR). GAP-43 was present in the cytoplasm, accumulating in the perinuclear area. An increase in GAP-43 expression was observed with a peak at 10 h at the mRNA level and at 12 h at the protein level, after exposure to the magnetic field. The increased level of GAP-43 protein returned to a normal level within 24 h of exposure to a 5 mT magnetic field. The kinetic pattern of GAP-43 expression induced by X-ionizing radiation was very similar to that induced by the magnetic field. These results suggest that the stimulation of GAP-43 expression could occur by a similar mechanism following exposure to X-rays or magnetic fields. We have provided the first evidence that exposure to a 5 mT magnetic field can induce GAP-43 gene expression in human glioma MO54 cells.