Melatonin Secretion and Puberty in Female Lambs Exposed to Environmental Electric and Magnetic Fields1

Abstract

This study determined whether chronic exposure of female lambs to the electric and magnetic fields (EMF) of a high voltage transmission line can alter pineal secretion of melatonin and the normal occurrence of puberty. Twenty female Suffolk lambs were assigned randomly in equal numbers to a control and a treatment group. Treatment from 2 to 10 mo of age consisted of continuous exposure within the electrical environment of a 500-kV transmission line (mean electric field 6 kV/m, mean magnetic field 40 mG). Treated lambs were penned directly beneath the transmission line; control lambs were maintained in a pen of similar construction 229 m from the line where EMF were at ambient levels (mean electric field < 10 V/m, mean magnetic field < 0.3 mG). Melatonin was analyzed by RIA in serum of blood samples collected at 0.5-3-h intervals over eight 48-h periods. To assess attainment of puberty, serum concentrations of progesterone were determined by RIA from blood samples collected twice weekly beginning at 19 wk of age. Concentrations of circulating melatonin in control and treated lambs were low during daylight hours and increased during nighttime hours. The characteristic pattern of melatonin secretion during nighttime (amplitude, phase, and duration) did not differ between control and treatment groups. Age at puberty and number of subsequent estrous cycles also did not differ between groups. These data suggest that chronic exposure of developing female sheep to 60-Hz environmental EMF does not affect the mechanisms underlying the generation of the circadian pattern of melatonin secretion or the mechanisms involved in the onset of reproductive activity.

The Melatonin Hypothesis: Electric Power and Breast Cancer

“…There have also been reports that such fields have little or no effect (31)(32)(33). AC magnetic fields as low as 10 mG have been reported to suppress melatonin in rats (29,30).…”

Environmental and social impacts of electricity utilization: broadening the debate

“…No significant changes in nocturnal plasma melatonin were noted in 12-h photoperiods (Burchard et al 1998) or in 8-h daylengths (Rodriguez et al 2004), but plasma melatonin levels were slightly lower during the light periods in these exposed animals and plasma prolactin was increased in lactating pregnant cows in short day conditions. The influence of 60-Hz EMF environments on melatonin in laboratory animals could not be confirmed by studies on sheep exposed to high-voltage electricity transmissionline environments (Lee et al 1993. However, cortisol levels declined in both control and experimental animals following their movement to the proximity of the experimental site (Figs.…”

Nocturnal urinary melatonin levels and urine biochemistry in microwave-irradiated rats

“…It appears that EMFs suppress different components of melatonin secretion and metabolism (Grota et al 1994;Brainard et al 1999;Fernie et al 1999;Brendel et al 2000). On the other hand, chronic exposure of lambs to the environmental electric and magnetic fields has failed to affect the mechanisms behind the circadian pattern of melatonin secretion (Lee et al 1993). Additionally, Stärk et al (1997) pointed towards the absence of any effect of chronic RF exposure on salivary melatonin concentrations in cattle, concordant to the Vollrath's group who found no short-term effects of high frequency RF exposure on mammalian pineal gland and melatonin synthesis (Vollrath et al 1997).…”