Changes in neurite outgrowth but not in cell division induced by low EMF exposure: influence of field strength and culture conditions on responses inrat PC12 pheochromocytoma cells

The effects of low electromagnetic field (EMF) exposure (4.5-15.8 muT, 50 H z AC) on neurite outgrowth and cell division in rat PC12 pheochromocytoma c ells were examined. The study involved two separate experimental series in which culture conditions during exposure to the magnetic fields differed. I n series 1 (14 experiments in which culture conditions were not strongly co nducive to cell differentiation [15% serum]), exposure to 4.5-8.25 muT for 23 h significantly inhibited neurite outgrowth by 21.5 +/- 1.3% (by Manova, p = 0.003). In contrast, in series 2 (12 experiments in which culture cond itions promoted cellular differentiation [4% serum]), exposure to 4.35-8.25 muT for 23 h significantly stimulated neurite outgrowth by 16.9 +/- 1.1% ( by Manova, p = 0.009). Thus, in both series, exposure to a narrow range of low EMF has significant, but opposite effects on neurite outgrowth. Exposur e to higher fields, 8.25-12.5 muT (series 1) and 8.25-15.8 muT (series 2) h ad no significant effect on neurite outgrowth. These data, when considered with other reports, suggest that neuronal differentiation can be altered by low level EMF exposure. While this may not be detrimental, it merits furth er research. At present, the reasons for the significant changes in neurite outgrowth being confined to the same narrow field strength are unclear. As stated above, culture conditions in series 2 were more conducive to cell d ifferentiation than those in series 1. This is reflected in the lower numbe r of cells in control samples in series 2, at the end of the 23-h incubatio n, than in series 1 (-16.9 +/- 1.7%, p = 0.003). As the same numbers were p lated in both series, the medium used in series 1 allows more of the PC12 c ells to divide; this is consistent: with some cells reverting to a non-neur onal adrenal chromaffin phenotype [L. Greene, A. Tischler. Establishment of a noradrenergic clonal line of rat adrenal pheochromocytoma cells which re spond to nerve growth factor. Proc. Natl. Acad. Sci. U. S. A., 73 (1976) 24 24-2426]. Exposure to both ranges of magnetic fields (4.35-8.25 and 8.25-15 .8 muT) has no effect on cell division. Thus, there is no evidence in this study that there is a mitogenic effect arising from low EMF exposure. (C) 2 000 Elsevier Science S.A. All rights reserved.