Magnetic field (50 Hz) increases N-acetyltransferase, hydroxy-indole-O-methyltransferase activity and melatonin release through an indirect pathway.

Purpose: To examine whether magnetic fields (MF) affect N-acetyltransferase (NAT) and hydroxy-indole-O-methyltransferase (HIOMT) activity directly or exert their effect through a cellular pathway that indirectly regulates the activity of these enzymes and melatonin release.

Materials And Methods: The pineal glands from Wistar rats were isolated at 10:00 h and exposed to MF (50 Hz, 1 mT) for 4 h in vitro, with or without 1 micro M norepinephrine. An additional group of pineals was exposed to MF 30 min before norepinephrine addition. The direct effect of MF on the activity of the enzymes was studied in sonicated glands exposed to MF. NAT activity, HIOMT activity and melatonin release were determined.

Results: In pineal glands isolated in the morning, 4-h in vitro exposure did not affect the basal release of melatonin from the pineal gland as well as the basal NAT and HIOMT activities. Pineal gland exposure to MF 30 min before norepinephrine addition significantly (p<0.05) increased NAT activity, HIOMT activity and melatonin release (p<0.05). These effects were not observed in pineals co-treated with MF and norepinephrine or in sonicated glands exposed to MF.

Conclusions: The results suggest that in pineals isolated in the morning, 4-h MF exposure changes melatonin release by affecting the signal transduction pathway leading from the norepinephrine receptor to NAT and HIOMT and not via a direct effect at the enzyme levels.