SUMMARY
The effects of irradiation (200kV X-ray, 5 Gy), extremely low frequency electromagnetic fields
(ELF-EMF, 50 Hz, 60 ± 0.2 microT) and/or heat shock (HS, 41°C for 30 min) on the expression of
several heat shock genes (HSP27, HSP60, HSP70, HSP75, HSP78, HSP90) in human HL-60
leukaemia cells was studied by RT-PCR. In addition, the effects of these stressors on cell cycle
progression in exponentially and asynchronously growing cell cultures were studied by flow
cytometry. The dynamics of cell division during successive cell cycles was monitored by
fluorescence-labelling of the cells with carboxyfluorescein succinimidyl ester (CFSE). Finally, the
cell cycle distribution was studied by staining with propidium iodide (PI). With respect to HSP gene
expression the three stressors produced similar effects. The combination of stressors (ELF-EMF and
HS or Radiation and HS) strongly induced transcription of the HSP70 gene above the level induced
by each stressor alone. The cell cycle analysis, however, revealed striking differences in the cellular
response to each stressor. Of particular interest was the observed thermoprotective effect of ELFEMF
in heat shocked cells, an effect that was not seen in cells which were exposed to X-rays in the
presence of thermal stress.
KEY WORDS
electromagnetic fields; heat shock; radiation; thermoprotection; X-rays
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CITED
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