INCREASED LEVELS OF HSP70 TRANSCRIPTS INDUCED WHEN CELLS ARE EXPOSED TO LOW-FREQUENCY ELECTROMAGNETIC-FIELDS

Previous experiments have shown that the steady state levels of some RNA transcripts are increased when cells are exposed to extremely low frequency electric or magnetic fields. Experiments have exposed a variety of cell types, including dipteran salivary gland cells, yeast and human HL-60 cells. The range of responsive transcripts includes oncogenes such as c-myc, as well as transcripts associated with growth and development. One hypothesized mechanism of how cells respond to electromagnetic (EM) fields assumes that the response represents or mimics a generalized physiological stress response. RNA from exposed HL-60 cells, previously shown to have increased transcript levels for c-myc, was analyzed for hsp70 transcripts levels. The hsp70 transcripts were found to be elevated in ail cases, even though the cells were exposed to various fields at normal growth temperatures. The conditions of maximum induction for hsp70 were coordinate with those of c-myc. In yeast cells, the SSA1 gene (homologous to hsp70) was found to be elevated in cells exposed to EM fields at 0.8-80 mu T. In the case of yeast, conditions for maximum induction of SSA1 were coordinate with those for URA3, the gene for uracil metabolism. Thus the model of cell interaction with electric and/or magnetic fields appears to be related to the stress response model for heat shock.