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Title: Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields

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 notmore » 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.« less

Authors:
; ; ; ; ; ; ; ;  [1]
  1. (Oregon State Univ., Corvallis (United States))
Publication Date:
OSTI Identifier:
5505956
Resource Type:
Journal Article
Resource Relation:
Journal Name: Biology of Reproduction; (United States); Journal Volume: 49:4
Country of Publication:
United States
Language:
English
Subject:
63 RADIATION, THERMAL, AND OTHER ENVIRON. POLLUTANT EFFECTS ON LIVING ORGS. AND BIOL. MAT.; ELECTROMAGNETIC FIELDS; BIOLOGICAL EFFECTS; FEMALES; ESTROUS CYCLE; MELATONIN; SECRETION; SHEEP; BLOOD CHEMISTRY; CHRONIC EXPOSURE; DAILY VARIATIONS; ENVIRONMENTAL EXPOSURE; LIFE CYCLE; PINEAL GLAND; PROGESTERONE; AMINES; ANIMALS; AROMATICS; AZAARENES; AZOLES; BIOCHEMISTRY; BODY; CHEMISTRY; DOMESTIC ANIMALS; GLANDS; HETEROCYCLIC COMPOUNDS; HORMONES; INDOLES; KETONES; MAMMALS; ORGANIC COMPOUNDS; ORGANIC NITROGEN COMPOUNDS; ORGANS; PREGNANES; PYRROLES; RUMINANTS; STEROID HORMONES; STEROIDS; TRYPTAMINES; VARIATIONS; VERTEBRATES; 560400* - Other Environmental Pollutant Effects

Citation Formats

Lee, J.M. Jr., Stormshak, F., Thompson, J.M., Thinesen, P., Painter, L.J., Olenchek, E.G., Hess, D.L., Forbes, R., and Foster, D.L.. Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields. United States: N. p., 1993. Web. doi:10.1095/biolreprod49.4.857.
Lee, J.M. Jr., Stormshak, F., Thompson, J.M., Thinesen, P., Painter, L.J., Olenchek, E.G., Hess, D.L., Forbes, R., & Foster, D.L.. Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields. United States. doi:10.1095/biolreprod49.4.857.
Lee, J.M. Jr., Stormshak, F., Thompson, J.M., Thinesen, P., Painter, L.J., Olenchek, E.G., Hess, D.L., Forbes, R., and Foster, D.L.. Fri . "Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields". United States. doi:10.1095/biolreprod49.4.857.
@article{osti_5505956,
title = {Melatonin secretion and puberty in female lambs exposed to environmental electric and magnetic fields},
author = {Lee, J.M. Jr. and Stormshak, F. and Thompson, J.M. and Thinesen, P. and Painter, L.J. and Olenchek, E.G. and Hess, D.L. and Forbes, R. and Foster, D.L.},
abstractNote = {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.},
doi = {10.1095/biolreprod49.4.857},
journal = {Biology of Reproduction; (United States)},
number = ,
volume = 49:4,
place = {United States},
year = {Fri Oct 01 00:00:00 EDT 1993},
month = {Fri Oct 01 00:00:00 EDT 1993}
}
  • In an earlier study, the authors found no effects of 60 Hz electric and magnetic fields (EMF) from a 500 kV transmission line on serum melatonin patterns or on puberty in ten female Suffolk lambs (Ovis aries). The authors conducted a larger replicate study of 15 lambs exposed to a mean electric field of 6.3 kV/m and a mean magnetic field of 3.77 {mu}T and 15 controls exposed to EMF two orders of magnitude weaker than in the line area. The replicate produced essentially the same results as their previous study.
  • Although several kinds of biological effects of electric and magnetic fields have been reported from laboratory studies, few have been independently replicated. When this study was being planned, the suppression of nighttime melatonin in rodents was thought to represent one of the strongest known effects of these fields. The effect had been replicated by a single laboratory for 60-Hz electric fields, and by multiple laboratories for d-c magnetic fields. The primary objective of this study was to determine whether the effect of electric and magnetic fields on melatonin would also occur in sheep exposed to a high voltage transmission line.more » The specific hypothesis tested by this experiment was as follows: The electrical environment produced by a 60-Hz, 500-kV transmission line causes a depression in nocturnal melatonin in chronically exposed female lambs. This may mimic effects of pinealectomy or constant long-day photoperiods, thus delaying the onset of reproductive cycles. Results of the study do not provide evidence to support the hypothesis. Melatonin concentrations in the sheep exposed to the transmission line showed the normal pattern of low daytime and high nighttime serum levels. As compared to the control group, there were no statistically significant group differences in the mean amplitude, phase, or duration of the nighttime melatonin elevation.« less
  • Rats exposed to 60-Hz electric fields of either 10, 65, or 130 kV/m from conception to 23 days of age exhibited reduced peak nighttime pineal melatonin contents compared to unexposed controls. As a group, the exposed rats also exhibited a phase delay, estimated at approximately 1.4 hours, in the occurrence of the nocturnal melatonin peak. No clear dose-response relationship was noticed over the range of electric field strengths used as treatments in these experiments. These are the first studies concerned with the effects of electric field exposure on the pineal melatonin rhythm in immature rats. The findings are generally consistentmore » with those obtained using adult rats, where electric field exposure has been shown to abolish the nighttime rhythm in pineal melatonin concentrations.« less
  • An increased incidence and severity of a brownish coloration of hair has been observed around the nose and on the ears of female rats that were chronically exposed to 60-Hz electric fields. Microscopic examination of the colored areas revealed a red-brown globular deposit on hair shafts in affected areas without signs of physical injury.
  • The objective of this study was to determine whether daytime occupational exposure to extremely low frequency magnetic fields (MFs) suppresses nocturnal melatonin production. Sixty female volunteers were recruited. Thirty-nine worked in a garment factory, and 21 office workers served as a reference group. Exposure assessment was based on the type of sewing machine used and MF measurements around each type of machine. Eye-level MF flux density was used to classify the operators to higher (> 1 microT) and lower (0.3-1 microT) exposure categories. A third group of factory workers had diverse MF exposures from other sources. The reference group hadmore » average exposure of about 0.15 microT. Urine samples were collected on Friday and Monday for three consecutive weeks. Melatonin production was assessed as urinary 6-hydroxymelatonin sulfate (6-OHMS) excretion. The ratio of Friday morning/Monday morning 6-OHMS was used to test the hypothesis that melatonin production is suppressed after 4 days of occupational MF exposure with significant recovery during the weekend. Possible chronic suppression of melatonin production was evaluated by studying exposure-related differences in the Friday values by multivariate regression analysis. The Monday/Friday ratios were close to 1.0, suggesting that there is no increase in melatonin production over the weekend. The average 6-OHMS excretion on Friday was lower among the factory workers than in the reference group, but no monotonous dose-response was observed. Multivariate regression analysis identified MF exposure, smoking, and age as significant explanatory variables associated with decreased 6-OHMS excretion.« less