title: Effects of selenium overexposure on glutathione peroxidase and thioredoxin reductase gene expressions and activities.
abstract: Selenium (Se) is an essential trace element in animals and human, however, excess Se intake can result in adverse health effects. Se supplementation increased glutathione peroxidase (GSH-Px) and thioredoxin reductase (TR) expressions in Se-deficient rats. However, little information is available on the relationship between Se overexposure on GSH-Px and TR mRNA levels and activities. In this study, the effects of Se overexposure on GSH-Px and TR mRNA levels and activities were investigated by reverse transcription-polymerase chain reaction (RT-PCR) and activity assay. Experimental groups of male Wistar rats were injected intraperitoneally (i.p.) with sodium selenite at doses of 20, 40, and 80 microg Se/kg/d for 15 d, respectively. Se levels were elevated dose-dependently in rat liver, kidney, and testis tissues. GSH-Px mRNA levels and activities in the liver and testis for rats injected with 20 microg Se/kg/d were increased significantly as compared with those in the control group. However, intraperitoneal injection of 40 and 80 microg Se/kg/d dramatically decreased GSH-Px mRNA expression and activity in liver and testis. The changes of TR mRNA level and activity in the liver and kidney were similar to those of GSH-Px in the liver and testis when supplemented with 40 and 80 microg Se/kg/d. There were no significant effects of Se status on kidney GSH-Px and testis TR expressions. The results suggested that Se overexposure had an adverse effect on GSH-Px and TR mRNA levels and activities, and there could be tissue differences in the regulation of selenoprotein levels.
authors.affiliation: Department of Chemistry, Huazhong University of Science and Technology, Wuhan, People's Republic of China.
authors.forename: Lu
authors.initials: L
authors.lastname: Gan
authors.forename: Qiong
authors.initials: Q
authors.lastname: Liu
authors.forename: Hui-Bi
authors.initials: HB
authors.lastname: Xu
authors.forename: Yu-Shan
authors.initials: YS
authors.lastname: Zhu
authors.forename: Xiang-Liang
authors.initials: XL
authors.lastname: Yang
mesh_terms: D000818:Animals; D015971:Gene Expression Regulation, Enzymologic / Q000187:drug effects*; D005979:Glutathione Peroxidase / Q000235:genetics* / Q000378:metabolism*; D007668:Kidney / Q000187:drug effects; D008099:Liver / Q000187:drug effects; D008297:Male; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012643:Selenium / Q000008:administration & dosage / Q000633:toxicity*; D013737:Testis / Q000187:drug effects; D013880:Thioredoxin-Disulfide Reductase / Q000235:genetics* / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger; D005979:Glutathione Peroxidase; D013880:Thioredoxin-Disulfide Reductase; D012643:Selenium