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 DOI: 10.1191/0748233705th212oa

2005 21: 27Toxicol Ind HealthDelibas

Ahmet Koyu, Fehmi Ozguner, Gokhan Cesur, Osman Gokalp, Hakan Mollaoglu, Sadettin Caliskan and Namiknocturnal serum melatonin levels in rats

No effects of 900 MHz and 1800 MHz electromagnetic field emitted from cellular phone on  

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No effects of 900 MHz and 1800 MHz electromagnetic field emitted from

cellular phone on nocturnal serum melatonin levels in rats

Ahmet Koyua, Fehmi Ozgunera, Gokhan Cesura, Osman Gokalpb, Hakan Mollaoglua, SadettinCaliskana and Namik Delibasc

aDepartment of Physiology, Suleyman Demirel University, School of Medicine, Isparta, TurkeybDepartment of Pharmacology, Suleyman Demirel University, School of Medicine, Isparta, TurkeycDepartment of Biochemistry and Clinical Biochemistry, School of Medicine, Isparta, Turkey

In this study, the effects of exposure to a 900 MHz and 1800 MHz electromagnetic field (EMF) onserum nocturnal melatonin levels of adult male Sprague�/Dawley rats were studied. Thirty rats were

used in three independent groups, 10 of which were exposed to 900 MHz, 10 of which were exposed

to 1800 MHz and 10 of which were sham-exposed (control). The exposures were performed 30 min/

day, for five days/week for four weeks to 900 MHz or 1800 MHz EMF. Control animals were kept

under the same environmental conditions as the study groups except with no EMF exposure. The

concentration of nocturnal melatonin in the rat serum was measured by using a radioimmunoassay

method. There were no statistically significant differences in serum melatonin concentrations

between the 900 MHz EMF group and the sham-exposed group (P�/0.05). The values at 12:00 pmwere 39.119/6.5 pg/mL in the sham-exposed group and 34.979/5.1 pg/mL in the 900 MHz EMF-

exposed group. Also, there were no statistically significant differences in serum melatonin

concentrations between the sham-exposed group and the 1800 MHz EMF-exposed group (P�/

0.05). The values at 12:00 pm were 39.119/6.5 pg/mL in the sham-exposed group and 37.969/7.4

pg/mL in the exposed group. These results indicate that mobile phones, emitting 900

and 1800 MHz EMF, have no effect on nocturnal serum melatonin levels in rats. Toxicology and

Industrial Health 2005; 21: 27�/31.

Key words: 900 and 1800 MHz electromagnetic field; nocturnal serum melatonin

Introduction

There is growing public concern that radiofre-

quency electromagnetic fields (EMFs) may have

adverse biological effects. Furthermore, there is

accumulating evidence that exposure to the radio-

frequency fields from mobile telephones or their

base stations could affect health (Heikkinen et al .,

2003). Such has been the rapid growth of mobile

telecommunications that there will be about one

billion mobile phone users before 2005. Therefore,

if there were any impact of mobile telephones on

health, it would affect almost everyone in the world

(Repacholi, 2001).At present, most of the mobile phones in Europe

generally work at a frequency of 900 MHz and 1800

MHz in the GSM systems. The cellular responses to

various forms of radiation, including ionizing, UV

radiation or exposure to EMFs are manifested as

Address all correspondence to: Ahmet Koyu, Suleyman DemirelUniversity, School of Medicine, Department of Physiology, 32260Isparta, TurkeyE-mail: ahmetkoyu@tnn.net

Toxicology and Industrial Health 2005; 21: 27�/31

www.tihjournal.com

# 2005 Edward Arnold (Publishers) Ltd 10.1191/0748233705th212oa

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reversible or irreversible from structural to func-tional changes (Cox, 2003; Rothman et al ., 1996;Somosy, 2000). Over the past two decades, there hasbeen increasing interest in the biological effects andpossible health outcomes of the weak, high-fre-quency electric and magnetic fields (Knave, 2001).Some studies on the magnetic fieldsand cancer, reproduction and neurobehaviouralreactions have suggested that different system dis-eases are related to EMFs such as those similar toones produced by mobile phones (Bartsch et al .,2002; Bortkiewicz, 2001; Cox, 2003; Knave, 2001;Leszczynski et al ., 2002).

Melatonin, mainly synthesized in the pinealgland lying near the centre of the brain, is ahormone with a characteristic circadian secretorypattern, with little secretion during daytime and astrikingly increased synthesis at night. It has antic-arcinogenic (Lissoni, 2000; Rao et al ., 2000) andfree radical scavenging (Qi et al ., 2001; Wakatsukiet al ., 2001) properties. Short pulses of light duringthe night time can rapidly inhibit melatonin synth-esis, but during the daytime the retina�/hypothala-mus pineal system is refractory to darkness. Inaddition to light, melatonin synthesis is known tobe suppressed in animals by inverted static geo-magnetic fields or extremely low frequency sinusoi-dal magnetic fields (Reiter, 1993). As the pinealgland is located in the brain and during normal usemore than 50% of the radiation from mobile phoneshas been proved to be absorbed in the human brain(Martens, 1994), it stood to reason to study the invivo effect of exposure to EMF at 900 MHz and1800 MHz frequency GSM-like modulated wave-forms on the pineal gland. So far there has beenremarkably little research carried out to test theeffects of GSM-like EMF on melatonin secretion.

The aim of this study was to investigate whetherthe serum nocturnal melatonin levels of adult maleSprague�/Dawley rats could be altered after expo-sure to the 900 MHz and 1800 MHz GSM-likeEMF generator.

Material and methods

Study protocol

The animals used in this study were procured,maintained and used in accordance with the

Animal Welfare Act and the Guide for the Careand Use of Laboratory Animals prepared by theAnimal Ethical Committee, Suleyman DemirelUniversity. Thirty male Sprague�/Dawley rats(12 weeks old, each weighing 250�/300 g at the startof the experiment) were maintained under a12-h light/dark cycle in a temperature-regulated(239/18C) animal room with continuous free accessto water and food.

Animals were randomly grouped as follows:control (sham-exposed) group (n�/10), 900 MHzEMF (n�/10) and 1800 MHz EMF groups (n�/10).The rats of control group received no radiationexposure while the rats of 900 MHz and 1800 MHzgroups were exposed to 30 min/day radiation for aperiod of five days per week. The radiationexposure lasted for four weeks.

At the end of four weeks, the rats were sacrificedat 12:00 pm and blood samples were collectedthrough a cardiac puncture.

Experimental set-up and radio frequency irradiation

The exposure system consisted of a round plastictube cage (length: 12 cm, diameter: 5.5 cm) and adipole antenna (as shown in Figure 1). The wholebody of the rat was positioned in close contactabove the dipole antenna, and the tube wasventilated from head to tail in order to decreasethe stress of the rat while in the tube.

A 900 and 1800 MHz continuous wave electro-magnetic energy generator (the peak specific ab-sorption rate (SAR) was 2 W/kg, average powerdensity 19/04 mW/cm2) produced at the electro-magnetic compatibility (EMC) laboratory of Suley-man Demirel University was used in the study. Thepower density measurements were made using anEMF meter (Holaday Industry, Inc., Adapazarı,

Rat

12 cm

5.5cm

Half wave dipole antenna

900 −1800 MHz EMF Generator

Figure 1. Schema of EMF (900�/1800 MHz) exposure device.

No effects of electromagnetic field on serum melatoninA Koyu et al .

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Turkey). Rats who were exposed for 30 min/day, for5 days/week for four weeks to a 900 MHz or 1800MHz EMF were compared to control rats withrespect to serum melatonin levels.

Serum melatonin radioimmunoassay (RIA)

Blood samples were collected into glass tubeswithout anticoagulant and were allowed to clot.They were centrifuged to obtain serum and storedat �/208C until the assay. Melatonin levelswere measured using a 125I-melatonin RIA kit(Biosource, Nivelles, Belgium).

Statistical analysis

SPSS 9.00 for Windows was used for statisticalevaluation in the study. Mann�/Whitney U-test wasperformed to analyse the data. The results of serummelatonin levels were given as mean9/SD. The limitof statistical significance was PB/0.05, two-side.

Results

The effect of 900 MHz and 1800 MHz GSM-likeEMF exposure on serum melatonin levels of adultmale Sprague�/Dawley rats was studied in threeindependent experiments. Figure 2 shows averageserum melatonin concentrations of the 900 MHzEMF group and sham-exposed group at 12:00 pm.As seen in the figure, the melatonin concentrationsof the rats exposed to the magnetic field weremarginally lower than those of the sham-exposedrats. However, there were no significant differencesin serum melatonin concentrations between the

sham-exposed rats and the rats exposed to themagnetic field (P�/0.05, by Mann�/Whitney U-Test). The values at 12:00 pm were 39.119/6.5 pg/mL in the sham-exposed group and 34.979/5.1 pg/mL in the exposed group.

The average serum melatonin concentrations ofthe 1800 MHz EMF group and sham-exposedgroup at 12:00 pm are presented in Figure 3.From the figure, it can be seen that the melatoninconcentrations in the rats exposed to the magneticfield were marginally lower than in the sham-exposed rats. However, there were no significantdifferences in serum melatonin concentrations be-tween the sham-exposed rats and those exposedto the magnetic field (P�/0.05, by Mann�/

Whitney U-Test). The values at 12:00 pm were39.119/6.5 pg/mL in the sham-exposed group and37.969/7.4 pg/mL in the exposed group.

Discussion

Frequency is the rate at which EMFs changedirection, and is measured in Hertz (Hz). Onemega hertz (MHz) is one million cycles per second.Analogue telephones use frequencies between 800and 900 MHz; and digital telephones use frequen-cies between 1800 and 1990 MHz; while microwaveovens use a frequency of 2450 MHz. Today’s mobiletelephones, with a total power output of 2 W, areestimated to produce insignificant local heating,which is unlikely to produce any deleterious effects.

It is known that the effect and the amount ofdamage caused by radiation are positively corre-lated with the exposure time (Moustafa et al .,2001).

0

5

10

15

20

25

30

35

40

45

50

Sham-exposed 900 MHz EMF

Groups

lm/

gpninotale

m

Figure 2. A comparison of average melatonin with SD between900 MHz EMF and sham-exposed at 12:00 pm. P�/0.05.

0

5

10

15

20

25

30

35

40

45

50

Sham-exposed 1800 MHz EMF

Groups

lm/

gpninotale

m

Figure 3. A comparison of average melatonin with SD between1800 MHz EMF and sham-exposed at 12:00 pm. P�/0.05.

No effects of electromagnetic field on serum melatoninA Koyu et al .

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We studied the effect of two GSM-like frequency

EMFs on nocturnal serum melatonin levels of rats.

Our results did not show significant difference in

the level of serum melatonin between the sham-

exposed group and the exposed group after 30 days

of exposure (30 min/day) to GSM-like EMF either

at 900 MHz or 1800 MHz frequency.There has been very little research on the effects

of magnetic fields on melatonin secretion, and the

investigations have been restricted to pulsed static

magnetic fields and very low-frequency EMFs. In

the previous studies, different effects of EMF on

pineal melatonin secretion have been reported. It

was reported that subchronic exposure of rats to a

50 Hz magnetic field decrease melatonin secretion

from pineal gland in rat (Kato et al ., 1993). It was

found that significant depression of nocturnal

melatonin rise was observed in humans under the

influence of exposure to a very low-frequency

magnetic field (2.9 mT, 40 Hz) for three weeks

(20 min per day, five days per week) (Karasek et al .,

1998). Moreover, Wilson et al . (1990) showed that

suppression of urinary 6-hydroxymelatonin sul-

phate levels occurred after exposure to EMF

emitted by continuous polymer wire electric field

blankets in some subjects. On the contrary, Mann

et al . (1998) observed no changes in several

endocrine parameters (GH, LH and melatonin) in

humans exposed to a 900 MHz electromagnetic

wave at night. It was shown that no changes

occurred in either serum melatonin or in urine

6-hydroxymelatonin sulphate levels in young men

after acute exposure (nine hours from 23:00 to

08:00 h) to 50 Hz linearly polarized MF (10 mT)

studies (Selmaoui et al ., 1996).It was hypothesized that extremely low frequency

(40�/50 Hz) EMF could suppress melatonin pro-

duction of pineal gland (Reiter, 1992; Stevens,

1987).Our findings are in agreement with the finding of

similar previous studies in humans (de Seze et al .,

1999; Mann et al ., 1998; Radon et al ., 2001) and

rodents (Bakos et al ., 2003; Heikkinen et al ., 1999;

Vollrath et al ., 1997) on other rodents at 900 MHz

GSM frequency EMF.Furthermore, the mobile telephone-emitted 900

MHz and 1800 MHz radiation is also absorbed by

skin more than internal organs (Riu et al ., 1997;

Sato et al ., 1999). Skin may have a protective role in

these frequencies for pineal gland. Also, in anotherstudy, it has been shown that radiation treatment at915 MHz causes erythema, oedema and ulcerationin human skin (Engin et al ., 1995).

So, we can speculate that the protection of thepineal gland from mobile phones may be explainedby the results of Riu et al. (1997), Sato et al . (1999)and Engin et al. (1995), which showed that inmobile telephones the radiation emitted at 900MHz and 1800 MHz radiation could absorbed byskin more efficiently than by internal organs.

In conclusion, it should not be concluded fromour studies that high-frequency EMFs produced bydigital mobile radio telephones have no influenceon the pineal gland under the conditions used. Thisdoes not mean that a significant effect might not beobserved, especially at the 900 MHz level, if a largernumber of animals were studied or if the durationof exposure was longer. Thus, further investigationsare needed to clearly show melatonin suppressionby EMFs of high frequency.

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