Horizontal or vertical 50-Hz, 1-microT magnetic fields have no effect on pineal gland or plasma melatonin concentration of albino rats.

Three experiments were carried out on male Wistar-King rats to determine if 6 weeks of exposure to horizontally- or vertically-oriented 1-microT, 50-Hz magnetic fields suppresses melatonin content in plasma and pineal gland, as does 6 weeks of exposure to circularly-polarized, 50-Hz, 1-microT magnetic fields. In each experiment, a concurrent sham-exposed control group was exposed to a stray field of 0.02 microT. In addition, a separate control experiment was completed between the horizontal and vertical field experiments in which cage-controls were housed in the exposure facility for 6 weeks without activation of the magnetic field coils. Subjects were sacrificed at 12:00 or at 24:00 h for collection of plasma and pineal gland; melatonin was determined by radioimmunoassay. In contrast to the results of experiments with rotating-vector magnetic fields, there were no significant differences among 1-microT, 0.02-microT and control groups in melatonin concentration of pineal gland or plasma.