title: Protection of rat chromosomes by melatonin against gamma radiation-induced damage.
abstract: The aim of this study was to investigate the protective effect of melatonin (2.5mg/kg/day, given to rats five times by intra-peritoneal injection) against damage in bone-marrow chromosomes induced by a single dose of gamma radiation (4.0 Gy whole-body irradiation; WBI). Ninety-six male albino rats were divided into four equal groups of 24 rats each. They were designated as I-non-irradiated, non-treated control rats, II-non-irradiated rats treated with melatonin for five successive days, III-whole-body gamma-irradiated rats and IV-rats injected with melatonin daily for five successive days, then subjected to whole-body gamma irradiation 2h after the final melatonin injection. Six rats from each group were sacrificed at days 1, 3, 7 and 10 following treatment and/or irradiation and their bone marrows were flushed out for micronuclei scoring and chromosomal analysis. WBI resulted in significant elevations in bone-marrow polychromatic erythrocytes containing micronuclei in their cytoplasm, and caused a significant decrease in the mitotic index of bone-marrow cells; in addition, there was a significant increase in the frequency of aberrant bone-marrow cells and in the different types of structural chromosomal aberration. Melatonin injection prior to WBI significantly reduced the mean frequencies of micro-nucleated polychromatic erythrocytes and of aberrant cells, as well as the incidence of structural chromosomal aberrations in bone-marrow cells; it also caused a highly significant elevation in the value of the mitotic index of bone-marrow cells. This investigation clarifies the protective and/or ameliorative role played by melatonin against deleterious effects of gamma radiation.
authors.affiliation: Department of Forensic Medicine and Toxicology, Faculty of Veterinary Medicine, Menofiya University-Sadat City Branch, Egypt. memzat68@yahoo.com
authors.forename: Mohammad E
authors.initials: ME
authors.lastname: Assayed
authors.forename: A M
authors.initials: AM
authors.lastname: Abd El-Aty
mesh_terms: D000818:Animals; D016587:Antimutagenic Agents / Q000494:pharmacology*; D001854:Bone Marrow Cells / Q000528:radiation effects; D002869:Chromosome Aberrations; D002875:Chromosomes / Q000187:drug effects / Q000528:radiation effects; D004249:DNA Damage / Q000187:drug effects* / Q000528:radiation effects*; D005720:Gamma Rays; D008297:Male; D008550:Melatonin / Q000494:pharmacology*; D015162:Micronucleus Tests; D009152:Mutagenicity Tests; D011837:Radiation-Protective Agents / Q000494:pharmacology*; D051381:Rats; D017208:Rats, Wistar; D014916:Whole-Body Irradiation
chemical_list: D016587:Antimutagenic Agents; D011837:Radiation-Protective Agents; D008550:Melatonin