title: Sister chromatid exchange and micronuclei in human peripheral blood lymphocytes treated with thyroxine in vitro.
abstract: Thyroid hormones enhance the metabolic rate and the aerobic metabolism favoring oxidative stress, which is accompanied by induction of damage to cellular macromolecules including the DNA. The aim of the present study was to investigate the ability of thyroxine to induce sister chromatid exchange and micronuclei, and to modulate cell-cycle kinetics in cultured human lymphocytes. Eight experimental concentrations of thyroxine were used, ranging from 2 x 10(-9) to 0.5 x 10(-4)M. Treatment with thyroxine increased the frequency of SCE per cell at the higher concentrations (1.5 x 10(-6), 0.5 x 10(-5), 1.5 x 10(-5) and 0.5 x 10(-4)M). On the other hand, there were no significant aneugenic and/or clastogenic effects observed in the cytokinesis-block micronucleus assay. The results show that thyroxine acted as a relatively weak clastogen compared with the positive control N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). In addition to the genotoxic effects, two high concentrations of thyroxine decreased the mitotic index and caused cell-cycle delay. In conclusion, thyroxine exhibited weak clastogenic effects only at high concentrations. Therefore, effects in humans might appear in cases of acute thyroxine overdose.
authors.affiliation: Department of Biology, Faculty of Veterinary Medicine, University of Belgrade, Bul. Oslobodjenja 18, Belgrade, Serbia and Montenegro. n.djelic@ptt.yu
authors.forename: Ninoslav
authors.initials: N
authors.lastname: Djelić
authors.forename: Biljana
authors.initials: B
authors.lastname: Spremo-Potparević
authors.forename: Vladan
authors.initials: V
authors.lastname: Bajić
authors.forename: Dijana
authors.initials: D
authors.lastname: Djelić
mesh_terms: D002453:Cell Cycle / Q000187:drug effects; D002467:Cell Nucleus / Q000187:drug effects*; D002478:Cells, Cultured; D016207:Cytokines / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006801:Humans; D008214:Lymphocytes / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D015162:Micronucleus Tests; D012854:Sister Chromatid Exchange / Q000187:drug effects*; D013974:Thyroxine / Q000494:pharmacology*
chemical_list: D016207:Cytokines; D013974:Thyroxine