Influence of extremely low frequency electromagnetic fields on growth performance, innate immune response, biochemical parameters and disease resistance in rainbow trout, Oncorhynchus mykiss
Nofouzi K, Sheikhzadeh N, Mohamad-Zadeh Jassur D, Ashrafi-Helan J. Influence of extremely low frequency electromagnetic fields on growth performance, innate immune response, biochemical parameters and disease resistance in rainbow trout, Oncorhynchus mykiss. Fish Physiol Biochem. 2015 Apr 14. [Epub ahead of print].
The effects of extremely low frequency electromagnetic fields on rainbow trout growth performance, innate immunity and biochemical parameters were studied.
Rainbow trout (17-18 g) were exposed to electromagnetic fields (15 Hz) at 0.01, 0.1, 0.5, 5 and 50 µT, for 1 h daily over period of 60 days.
Growth performance of fish improved in different treatment groups, especially at 0.1, 0.5, 5 and 50 µT. Immunological parameters, specifically hemagglutinating titer, total antiprotease and α1-antiprotease levels in treatment groups, were also enhanced. Total protein and globulin contents in the serum of fish exposed to 0.1, 0.5, 5 and 50 µT were significantly higher than those in the control group. No significant differences were found in serum enzyme activities, namely aspartate aminotransferase and alanine aminotransferase of fish in all treatment groups. Conversely, alkaline phosphatase level decreased in fish exposed to 0.01 and 50 µT electromagnetic fields. Meanwhile, electromagnetic induction at 0.1, 0.5, 5 and 50 µT enhanced fish protection against Yersinia ruckeri.
These results indicated that these specific electromagnetic fields had possible effects on growth performance, nonspecific immunity and disease resistance of rainbow trout.
Extremely low frequency electromagnetic fields (ELF-EMFs) originated from many sources such as household electric wiring, high voltage transmission lines and appliances have increased due to the high demand for electrical energy (Canseven et al. 2008). Anthropogenic sources of EMFs in the aquatic environment, such as subsea cables, are also increasing (Gill et al. 2012). With increase in EMF-producing equipment and environmental exposure, the hypothesis that EMF might have biological effects on human and/or on animal health has motivated scientists to direct their efforts toward understanding the biological influences of EMF. Many scientific studies verified that ELF-EMF can influence the biological systems, could involve principal changes in the cellular proliferation, stimulates ATP production, produces changes in the flow of ions through the membranes and increases CO2 formation in cellular cultures (Justo et al. 2006). In fact, biological effects of ELF-EMF have shown contradictory results. Several studies indicated an association between the exposure to ELF-EMF and suppression of immune system. For example, Cetin et al. (2006) showed that exposure to EMFs (60 Hz and 3 µT) for 12 h per day during 120 days had negative effects on mice marrow stem cells. Occupational exposure to ELF-MF exceeding 1 μT induced a reduction in NK activity in workers (Gobba et al. 2009). Meanwhile, long-term (4 days), continuous exposure of chick embryos to 60 Hz, 8 µT ELF-EMF caused lower HSP70 levels resulting in decline in cytoprotection, whereas short-time (20 min) exposure induced protection against hypoxia (Di Carlo et al. 2000). Exposure to ELF-EMF (50 Hz) at 0.5–1.5 mT for 45 min led to stimulation of murine macrophages (Simkó et al. 2001). Significantly elevated phagocytic activity, free radical release and IL-1β production of mouse macrophages by ELF-EMF (50 Hz and 1.0 mT) were also demonstrated (Frahm et al. 2006).
Effects of ELF-EMF on antioxidant system and biochemical parameters such as liver enzymes and metabolic products were also noted. ELF-EMF of 180–195 Hz and 120 µT decreased antioxidative enzyme activities and increased lipid peroxidation in 3T3-L1 preadipocyte cultures (Zwirska-Korczala et al. 2005). Electromagnetic fields of 50 Hz and 1.4 mT for 30 days caused body weight loss, lower glucose and total protein in mouse serum. Meanwhile, increase in lactate dehydrogenase activity was shown in mouse serum and liver (Hashish et al. 2008). Conversely, exposure to 50 Hz, 2 mT ELF-EMF for 2 months, 8 h/day, caused an increase in antioxidant enzyme levels in accordance with lower lipid peroxidation mouse red blood cells, liver and lungs (Singh et al. 1999). Exposure to ELF-EMF at 5 mT and 60 Hz attenuated insulin secretion from an islet-derived insulinoma cell line, RIN-m, by affecting calcium influx through calcium channels (Miyakoshi 2006).
There is some information regarding the biological effects of ELF-EMF exposure on fish species. Exposure to sinusoidal magnetic fields delayed the development of zebrafish (Danio rerio) embryos at 60 Hz and 0.1 mT (Cameron et al. 1985), and 50 Hz and 1 mT (Skauli et al. 2000). The lateral line of Anguilla anguilla showed an electrophysiological response to changes in EMF (Vriens and Bretschneider 1979; Moore and Riley 2009). Activity of locomotor muscles in Salmo salar altered with exposure to LF EMF (Richardson et al. 1976). Positive effects on growth and immune system in fantail goldfish caused by exposure to LF EMF signals (200–5000 Hz) between 0.15 and 50 µT intensities were also shown (Cuppen et al. 2007). In fact, anthropogenic EMF within the aquatic environment has only relatively recently come to be of interest, and scientific understanding of the consequences to species individuals, populations and ecosystem is slowly being identified and addressed (Gill et al. 2012). Considering previous studies, little is known regarding the possible effects of ELF-EMF exposure on fish growth, biochemical and immune parameters. Therefore, the present study was designed to delineate the possible roles of ELF-EMF with lower frequency (15 Hz) at field strengths 0.01, 0.1, 0.5, 5 and 50 µT, for 60 days on growth performance, innate immunity, serum-specific marker enzymes besides some serum metabolites and disease resistance against Yersinia ruckeri (Y. ruckeri) in juvenile rainbow trout.
Four hundred and fifty fish were distributed equally into six groups. Each group contained 25 fish in triplicates reared in individual glass aquarium. In treatment groups, fish were exposed to electromagnetic fields (15 Hz) in a range of 0.01 µT (T1 group), 0.1 µT (T2 group), 0.5 µT (T3 group), 5 µT (T4 group) and 50 µT (T5 group) induction for 1 h daily during 60 days. It must be noted that all aquariums were positioned in equally similar conditions regarding light intensity, temperature and background magnetic field intensity. No background AC noise was detected. Local earth magnetic field in location of all aquaria was measured using a Helmholtz coil and knowing the dip angle that was about 0.245 ± 0.003 Gauss (Maus et al. 2010) ...
In the present study, ELF-EMF exposure in treatment groups, especially in T4 and T5 groups, improved growth parameters. Similarly, continuous electromagnetic field of 361 Gauss per cm2 increased chick embryos’ weight at 15 days of age (Piera et al. 1992). Cuppen et al. (2007) also observed that broiler chickens exposed to ELF-EMF had improved feed conversion in comparison with control group. An increase in body weight after 10 weeks of exposure to a 0.5 mT magnetic field was also demonstrated in rats (Gerardi et al. 2008). Conversely, electromagnetic fields of 50 Hz and 1.4 mT for 30 days caused body weight loss in mice (Hashish et al. 2008). Some authors have attributed body weight differences in EMF-exposed animals to changes in eating habitat or metabolic changes (Hashish et al. 2008). Since in our study no differences were noted in eating habitat between all groups, it seems that metabolic changes might occur in treatment groups which lead to improved growth performance. In fish species, higher growth performance can happen by different mechanisms (Heidarieh et al. 2012). Influencing nutrient, especially protein digestibility by maintaining the function and structure of the small intestine, leads to an increased digestive capacity of the gut. Meanwhile, improved digestive enzymes, including lipase, amylase and protease, could result in better growth performances. In the present study, pathological examination did not show any differences in small intestine structure. Further studies to assess the digestive enzyme activities in fish exposed to ELF-EMF are warranted to elucidate the mechanisms through which ELF-EMF can affect the growth in fish species.
In the current study, higher survival rate against Y. ruckeri was also observed in rainbow trout exposed to ELF-EMF in T2, T3, T4 and T5 groups. Therefore, the stimulation of specific immune system and consequently protection against disease agents also occurred. Similar results were obtained by Maniu and Hritcu (2010) who noted higher antibody titer in rats exposed to ELF pulse electromagnetic field (50 Hz and 2.7 mT). Markov et al. (2006) also observed that EMF may enhance immune responses as evidenced by increased antibody levels and faster maturation of B lymphocytes.
Even though positive effects of ELF-EMF on immune system were shown in some studies, immune dysfunction by exposure to EMF should also be considered (Johansson 2009). Specific findings from studies on exposure to various types of EMFs report overreaction of the immune system, morphological alterations of immune cells, changes in lymphocyte viability, decreased count of natural killer cells and decreased count of T lymphocytes (Johansson 2009). For example, Cetin et al. (2006) showed that pulsed EMFs (60 Hz and 3 µT) for 12 h per day during 120 days negatively affected the hematological parameters of mice by reducing proliferation and differentiation of marrow stem cells.
Simkó and Mattsson (2004) presented a hypothesis of a possible initial cellular event by exposure to ELF-EMF. Based on their research, EMF exposure can cause both acute and chronic effects that are mediated by increased free radical levels. Short exposure to EMF leads to free radical production by phagocyting cells that positively lead to higher cytokine production. This mechanism can trigger both innate and specific immune system activations as indicated in previous studies. Conversely, an increase in the lifetime of free radicals by EMF leads to persistently elevated free radical production, subsequently causing negative effects such as DNA damage, tumor development and immune dysfunctions ...
It appears that there are many factors that influence the effects of ELF-EMF on animal performance, immune and biochemical values. They include the type of EMF, frequency, amplitude, timing and length of exposure. Therefore, inconsistent results have been achieved from studies on fish and other animals. However, EMF penetrates the animal body and acts on all organs, altering the cell membrane potential and distribution of dipoles and ions. These alterations influence all processes in animal body.
In general, besides numerous studies on disturbing the immune system and thus increasing disease after EMF exposure, the positive side of EMF use, which could be useful for specific therapeutic applications, should also be considered. In conclusion, this preliminary study showed that square wave ELF-EMF exposure at 15 Hz and intensities more than 0.5 µT may have beneficial effects in rainbow trout, thus affecting parameters such as growth performance, immunity and biochemical values. Further investigations are needed to fully understand the interaction between ELF-EMFs and different fish species even on the molecular level.
[My note: 0.5 µT is equivalent to 5 milligauss which is the magnetic field exposure 36 inches from a microwave oven.]
Joel M. Moskowitz, Ph.D., Director
Center for Family and Community Health
School of Public Health
University of California, Berkeley
Electromagnetic Radiation Safety
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