140
Electromagnetic Fields in Biological Systems
3.3.1.9 In Vivo Genotoxicity
Knowledge about the relationship between exposure to magnetic fields and generation
of free radicals in in vivo systems and in the cells is increasing. Regarding the role of
ROS and RNS in genotoxicity induced by magnetic fields, it has been reviewed that
free radical reactions are modulated by exposure to various magnetic fields of different
intensities and frequency ranges and the duration of such exposures: many fields result
in excitatory effects, some in inhibitory action, and others have no effect (Engström
2007; Simkó 2007; Okano 2008a,b). The magnetic fields influence (increase/decrease/
maintain) endogenous and exogenous ROS/RNS in in vivo, in vitro, and cell-free systems. However, magnetic field effects on pathogenesis and clinical relevance via ROS/
RNS have not been resolved. The underlying mechanisms of the modulation of ROS/
RNS induced by magnetic fields have not been clarified, although the relationship
between oxidative stress and hypertension and/or ischemia–reperfusion injury has been
implicated (see also Section 3.3.2.3).
Falone et al. (2008) examined whether the aging process can increase susceptibility toward widely present ELF-EMF-mediated prooxidative challenges. Female Sprague
Dawley rats were continuously exposed to an ELF-EMF (50 Hz, 0.1 mT) for 10 days. The
results indicated that ELF-EMF exposure significantly affects antioxidative capability
both in young and aged animals, although in opposite ways. Exposed young individuals
enhanced their neurotrophic signaling and antioxidative enzymatic defense against a
possible ELF-EMF-mediated increase in ROS. In contrast, aged animals underwent a
significant decrease in the major antioxidant enzymatic activities. The authors suggested that ELF-EMF acts as a risk factor for the occurrence of oxidative stress–based
nervous system pathologies associated with aging.
Yokus et al. (2008) investigated the genotoxic effect of an ELF-EMF (50 Hz, 100 and
500 μT, 2 h/day for 10 months) on oxidative DNA base modifications. In rat leukocytes,
levels of 8-hydroxyguanine (8-OH-Gua), 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua), and 4,6-diamino-5-formamidopyrimidine (FapyAde) were measured
following exposure to ELF-EMF. Levels of FapyAde, FapyGua, and 8OHdG in DNA
were significantly increased by 100-μT but not by 500-μT ELF-EMF compared with
the cage-control and the sham groups. The authors indicated that ELF-EMF generates
oxidatively induced DNA base modifications, which are mutagenic in mammalian cells,
such as FapyGua, FapyAde, and 8-OH-Gua. These findings support the hypothesis that
chronic exposure to 50 Hz EMFs may be potentially genotoxic. However, the intensity of
ELF-EMF has an important influence on the extent of DNA damage.
Torres-Duran et al. (2007) examined the effect of an ELF-EMF (60 Hz, 2.4 mT,
for 2 hours) on serum and liver lipid levels in rats. The results showed that ELF-EMF
increases the serum values of high-density lipoprotein cholesterol and the liver content
of lipoperoxides (measured as thiobarbituric acid reactive substances [TBARSs]) and
decreases total cholesterol in the liver. The same research group further evaluated the
effects of acute exposure to an ELF-EMF (60 Hz, 2.4 mT, for 2 hours), the application of
movement restraint, and the combination of both on antioxidant systems in the plasma,
liver, kidney, and heart of rats (Martinez-Samano 2010). Immediately after treatment,
reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and TBARS
Electromagnetic Fields in Biological Systems
3.3.1.9 In Vivo Genotoxicity
Knowledge about the relationship between exposure to magnetic fields and generation
of free radicals in in vivo systems and in the cells is increasing. Regarding the role of
ROS and RNS in genotoxicity induced by magnetic fields, it has been reviewed that
free radical reactions are modulated by exposure to various magnetic fields of different
intensities and frequency ranges and the duration of such exposures: many fields result
in excitatory effects, some in inhibitory action, and others have no effect (Engström
2007; Simkó 2007; Okano 2008a,b). The magnetic fields influence (increase/decrease/
maintain) endogenous and exogenous ROS/RNS in in vivo, in vitro, and cell-free systems. However, magnetic field effects on pathogenesis and clinical relevance via ROS/
RNS have not been resolved. The underlying mechanisms of the modulation of ROS/
RNS induced by magnetic fields have not been clarified, although the relationship
between oxidative stress and hypertension and/or ischemia–reperfusion injury has been
implicated (see also Section 3.3.2.3).
Falone et al. (2008) examined whether the aging process can increase susceptibility toward widely present ELF-EMF-mediated prooxidative challenges. Female Sprague
Dawley rats were continuously exposed to an ELF-EMF (50 Hz, 0.1 mT) for 10 days. The
results indicated that ELF-EMF exposure significantly affects antioxidative capability
both in young and aged animals, although in opposite ways. Exposed young individuals
enhanced their neurotrophic signaling and antioxidative enzymatic defense against a
possible ELF-EMF-mediated increase in ROS. In contrast, aged animals underwent a
significant decrease in the major antioxidant enzymatic activities. The authors suggested that ELF-EMF acts as a risk factor for the occurrence of oxidative stress–based
nervous system pathologies associated with aging.
Yokus et al. (2008) investigated the genotoxic effect of an ELF-EMF (50 Hz, 100 and
500 μT, 2 h/day for 10 months) on oxidative DNA base modifications. In rat leukocytes,
levels of 8-hydroxyguanine (8-OH-Gua), 2,6-diamino-4-hydroxy-5-formamidopyrimidine (FapyGua), and 4,6-diamino-5-formamidopyrimidine (FapyAde) were measured
following exposure to ELF-EMF. Levels of FapyAde, FapyGua, and 8OHdG in DNA
were significantly increased by 100-μT but not by 500-μT ELF-EMF compared with
the cage-control and the sham groups. The authors indicated that ELF-EMF generates
oxidatively induced DNA base modifications, which are mutagenic in mammalian cells,
such as FapyGua, FapyAde, and 8-OH-Gua. These findings support the hypothesis that
chronic exposure to 50 Hz EMFs may be potentially genotoxic. However, the intensity of
ELF-EMF has an important influence on the extent of DNA damage.
Torres-Duran et al. (2007) examined the effect of an ELF-EMF (60 Hz, 2.4 mT,
for 2 hours) on serum and liver lipid levels in rats. The results showed that ELF-EMF
increases the serum values of high-density lipoprotein cholesterol and the liver content
of lipoperoxides (measured as thiobarbituric acid reactive substances [TBARSs]) and
decreases total cholesterol in the liver. The same research group further evaluated the
effects of acute exposure to an ELF-EMF (60 Hz, 2.4 mT, for 2 hours), the application of
movement restraint, and the combination of both on antioxidant systems in the plasma,
liver, kidney, and heart of rats (Martinez-Samano 2010). Immediately after treatment,
reduced glutathione (GSH), catalase (CAT), superoxide dismutase (SOD), and TBARS