title: The influence of different light irradiances on pineal N-acetyltransferase activity and melatonin levels in the cotton rat, Sigmodon hispidus.
abstract: Wild-captured cotton rats (Sigmodon hispidus) trapped and tested in September and October exhibited a rapid reduction in pineal N-acetyltransferase (NAT) activity and melatonin levels after exposure to a light irradiance of 300 microW/cm2 during the dark period. The half-time for the depression of both NAT and melatonin was on the order of 2 min. The exposure of cotton rats during darkness to much lower irradiances of light, i.e., 5.0, 0.04, 0.03 or 0.01 W/cm2, for 32 min also greatly diminished pineal NAT activity and radioimmunoassayable melatonin levels; however, a light irradiance of 0.005 microW/cm2 failed to significantly depress either the acetylating enzyme or the melatonin content of the pineal gland. The results show that the pineal gland of the wild-captured cotton rat, as judged by NAT activity and melatonin levels, is inhibited even by very low irradiances of light.
mesh_terms: D000123:Acetyltransferases / Q000378:metabolism*; D000818:Animals; D003411:Arvicolinae / Q000378:metabolism*; D004307:Dose-Response Relationship, Radiation; D007700:Kinetics; D008027:Light; D008550:Melatonin / Q000378:metabolism*; D010870:Pineal Gland / Q000378:metabolism / Q000528:radiation effects*
chemical_list: D000123:Acetyltransferases; D008550:Melatonin