REDUCED PINEAL MELATONIN BIOSYNTHESIS IN FRACTIONALLY IRRADIATED RATS

Citation
E. Ahlersova et al., REDUCED PINEAL MELATONIN BIOSYNTHESIS IN FRACTIONALLY IRRADIATED RATS, Physiologia bohemoslovaca, 47(2), 1998, pp. 133-136
Citations number
18
Categorie Soggetti
Physiology
Journal title
ISSN journal
03699463
Volume
47
Issue
2
Year of publication
1998
Pages
133 - 136
Database
ISI
SICI code
0369-9463(1998)47:2<133:RPMBIF>2.0.ZU;2-Q
Abstract
The effects of ionizing radiation on pineal melatonin and on key enzym es of its metabolism have been studied in our laboratory. After adapta tion to an artificial light/dark cycle of 12:12 h, male Wistar rats we re fractionally whole-body irradiated with a dose of 2.4 Gy of gamma-r ays twice a week up to total doses of 4.8, 9.6 or 14.4 Gy. Irradiation and sham-irradiation were performed in the late afternoon. The rats w ere sacrificed at 24:00 to 01:00 h in darkness, 6 h, 3 or 5 days after the last exposure. Pineal and serum melatonin concentrations, pineal activities of serotonin N-acetyltransferase (NAT) and of monoamine oxi dase (MAO) were determined. The NAT activities in the rats irradiated with 4.8 and 9.6 Gy decreased at some intervals without changes of mel atonin concentration. Irradiation with a total dose of 14.4 Gy decreas ed NAT activity and the concentration of pineal and serum melatonin 6 h and 3 days after the last exposure. The activity of MAO, estimated o nly in the rats irradiated with the dose of 14.4 Gy, increased signifi cantly 3 days after irradiation. The fractionated irradiation up to th e dose of 14.4 Gy caused a transient decrease in pineal melatonin synt hesis. This could be the consequence of preferential oxidative deamina tion of serotonin in comparison with its N-acetylation, leading to mel atonin biosynthesis.