60 HZ MAGNETIC-FIELD EXPOSURE AND URINARY 6-SULPHATOXYMELATONIN LEVELS IN THE RAT

Four separate experiments were carried out to investigate the effect o f extremely low frequency magnetic field (MF) exposure (60 Hz, 1 mT rm s) on urinary 6-sulphatoxymelatonin (aMT6s) levels in Sprague-Dawley r ats. In the first experiment, immature male rats maintained under a re gular 12 h daily photoperiod (white fluorescent light) were exposed to a 20 h daily MF exposure for 6 weeks. The second experiment was simil ar to the first, except that the MF exposure was limited to 10 days. I n the third experiment, adult male rats acclimated to a combination of continuous dim red light and regular 12 h daily photoperiod (white fl uorescent) were subjected to a single 1 h exposure to intermittent MF (1 min on and 1 min off cycles), 2 h before fluorescent lights went of f. The fourth experiment was similar to the third, except that the ani mals received 2 consecutive days of 20 h daily exposure to intermitten t MF, beginning 1 h before the fluorescent lights went off each day. I n all four experiments, the circadian profile of urinary aMT6s was exa mined before, during, and after the MF exposure. No significant effect of 1 mT MF on indoleamine metabolism was observed in any of the above experiments. However, in one of the experiments (no. 4), both the con trol and the MF groups showed a lower aMT6s level during the exposure days, when compared with that of pre-and post-exposure days, suggestin g that the existence of possible effects with lower field strengths at the range of stray field cannot be ruled out. (C) 1998 Wiley-Liss, In c.