Short-term magnetic field exposures (60 Hz) induce protection against ultraviolet radiation damage

Purpose: To investigate the ability of electromagnetic (EM) field pre-exposures to induce protection in chick embryos against subsequent ultraviolet (UV) light exposure. Materials and Methods: Chick embryos in the 4th day of gestation were exposed for 20 minutes (short term) or 96 hours (long term) to 60 Hz, 8 mu T magnetic or sham fields (controls) followed by 30 minutes rest. They were then exposed to UV radiation of either low (30 J/m(2)) or high (45 J/m(2) ) intensity (long term was exposed only to 30 J/m(2)) for 75 minutes. Mortality measurements were made every 30 minutes following UV exposure. Results: At both UV intensities, short-term, EM field-exposed embryos showed significantly higher post-UV survival (p<0.05) at each time point as compared to controls. Long-term EM field exposures, however, offered no protection against low intensity UV light, in fact, 96 hour-EM field-exposed embryos were significantly less protected than non-EM field-exposed controls (p<0.05). Conclusions: Results of the present study demonstrate that EM field exposures of appropriate duration induce protection against damage from UV light exposure. Because EM field exposures have been reported to activate stress protein response pathways and protect against anoxia/re-oxygenation damage, stress proteins are thought to play a role in the observed UV protection.