Two-phase response of rat pineal melatonin to lethal whole-body irradiation with gamma rays.
Male Wistar rats adapted to artificial light:dark (LD) regimen 12:12 h were whole-body irradiated with a single dose of 9.6 Gy of gamma rays and sham/irradiated in the night in darkness. The rats were examined 60 min, 1, 3 and 5 days after exposure between 22:00 and 01:30 h in the darkness. The results obtained indicate a two-phase reaction of pineal melatonin after the lethal irradiation of rats: the decline of melatonin concentration early after the exposure (at 60 min) with unchanged serotonin N-acetyltransferase (NAT) activity followed by an increase of melatonin synthesis, accompanied by an increase of pineal and serum melatonin on day 5 after the exposure. NAT activity was increased on day 3 after the exposure. Serum corticosterone concentrations in irradiated rats were increased 60 min and 3 days after exposure. With respect to the antioxidant, immunomodulating and stress-diminishing properties of melatonin, we consider the increase in melatonin synthesis during later periods after irradiation as part of adaptation of the organism to overcome radiation stress.
Kassayová
M
M
Institute of Animal Physiology, Faculty of Science, P.J Safárik University, Kosice, Slovak Republic. kassaym@kosice.upjs.sk
Ahlersová
E
E
Ahlers
I
I
D000818:Animals; D008297:Male; D008550:Melatonin / Q000378:metabolism*; D010870:Pineal Gland / Q000378:metabolism* / Q000528:radiation effects; D051381:Rats; D017208:Rats, Wistar; D014916:Whole-Body Irradiation
D008550:Melatonin