title: Acute 60 Hz magnetic field exposure effects on the melatonin rhythm in the pineal gland and circulation of the adult Djungarian hamster.
abstract: Adult male and female hamsters in long days (16 hr of light) were exposed to a 1 gauss 60 Hz magnetic field for 15 min starting 2 hr before lights off. Sham-exposed controls were placed in an adjacent exposure system but current was not applied. Hamsters were decapitated at 0.5-2 hr intervals from 1 hr before lights off to 1 hr after lights on (n = 4-6/clocktime/group); sera were harvested and pineal glands obtained for melatonin radioimmunoassay. In controls, pineal melatonin significantly increased from an average daytime baseline of less than 0.3 ng/gland to 3 ng/gland by 3 hr after lights off (P < 0.05, ANOVA). This increase was sustained for the duration of the night and returned to baseline within 1 hr after lights on. A similar melatonin rhythm was found in serum; concentrations ranged from 30 to 50 pg/ml at night and returned to a baseline of 12 pg/ml or less by 1 hr before lights on. The single magnetic field exposure reduced the duration and blunted the rise in the nocturnal melatonin rhythm. The study was then repeated in its entirety 6 months later. The same magnetic field treatment significantly suppressed pineal melatonin content at 5 hr after lights off and reduced serum melatonin concentrations at 3 and 5 hr after dark onset compared to sham-exposed controls. Thus, the acute magnetic field exposure was again found to blunt the increase and suppress the duration of the nighttime melatonin rise.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Division of Perinatal Biology, Loma Linda University, School of Medicine, CA 92350.
authors.forename: S M
authors.initials: SM
authors.lastname: Yellon
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D006224:Cricetinae; D004574:Electromagnetic Fields; D005260:Female; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D017111:Phodopus; D010870:Pineal Gland / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D008550:Melatonin