ELECTRIC-FIELD EXPOSURE ALTERS SERUM MELATONIN BUT NOT PINEAL MELATONIN SYNTHESIS IN MALE-RATS

Sprague-Dawley male rats, maintained in a 14:10 h light:dark cycle wer e exposed for 30 days (starting at 56 days of age) to a 65 kV/m, 60 Hz electric field or to a sham field for 20 h/day beginning at dark onse t. Pineal N-acetyltransferase (NAT), hydroxy indole-o-methyl transfera se (HIOMT), and melatonin as well as serum melatonin were assayed. Pre liminary data on unexposed animals indicated that samples obtained 4 h into the dark period would reveal either a phase delay or depression in circadian melatonin synthesis and secretion. Exposure to electric f ields for 30 days did not alter the expected nighttime increase in pin eal NAT, HIOMT, or melatonin. Serum melatonin levels were also increas ed at night, but the electric field-exposed animals had lower levels t han the sham-exposed animals. Concurrent exposure to red light and the electric field or exposure to the electric field at a different time of the day-night period did not reduce melatonin synthesis. These data do not support the hypothesis that chronic electric field exposure re duces pineal melatonin synthesis in young adult male rats. However, se rum melatonin levels were reduced by electric field exposure, suggesti ng the possibility that degradation or tissue uptake of melatonin is s timulated by exposure to electric fields. (C) 1994 Wiley-Liss, Inc.