title: [Effects of hypoxic exposure on coordinative expression of cytochrome oxidase subunits I and IV in rat cerebral cortex].
abstract: This study was intended to evaluate the effects of hypoxic exposure on gene expression and coordination of cytochrome oxidase (COX) subunits I (COX I) and IV (COX IV) encoded by mtDNA and nDNA respectively in rat cerebral cortex. Male Wistar rats were exposed to hypoxia in a hypobaric chamber simulating high altitude at 5000 m for 2, 5, 15 and 30 d. Control rats were fed outside the hypobaric chamber (the height was 300 m above sea level). Rats were sacrificed and mitochondria from cerebral cortex were isolated by differential centrifugation at each time point. COX I and COX IV proteins in isolated rat cerebral cortex mitochondria were detected by Western blot analysis and mRNA in the cerebral cortex by RT-PCR. The ratios of protein and mRNA were used to estimate the coordinative expression of two subunits. The results showed that COX I mRNA increased significantly at 2 and 5 d, and decreased to the control level at 15 and 30 d; COX IV mRNA remarkably increased at 2, 5 and 15 d, and dropped below the control level at 30 d. The mRNA ratio of COX IV to COX I reached a peak at 15 d, but showed no differences between other time points. The Western blot analysis of COX I and COX IV in isolated rat cerebral cortex mitochondria showed no obvious changes during hypoxic exposure. Our findings demonstrate that hypoxia can affect mRNA expression of COX I and COX IV and their coordination, while protein expression of both subunits are stable and coordinative. This study suggests that the expression of COX I and COX IV proteins during hypoxic exposure is coordinately regulated by post-transcriptional mechanisms.
authors.affiliation: Department of Pathophysiology, College of High Altitude Military Medicine,the Third Military Medical University, Chongqing 400038; E-mail: liuliu@mail.tmmu.com.cn
authors.forename: Xiao-Ling
authors.initials: XL
authors.lastname: Tan
authors.forename: Jun-Ze
authors.initials: JZ
authors.lastname: Liu
authors.forename: Li-Fei
authors.initials: LF
authors.lastname: Cao
authors.forename: Zhong-Cai
authors.initials: ZC
authors.lastname: Deng
authors.forename: Ying-He
authors.initials: YH
authors.lastname: Li
mesh_terms: D000818:Animals; D002540:Cerebral Cortex / Q000378:metabolism*; D003576:Electron Transport Complex IV / Q000378:metabolism*; D015971:Gene Expression Regulation, Enzymologic; D000860:Hypoxia / Q000378:metabolism*; D008297:Male; D008928:Mitochondria / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar
chemical_list: D003576:Electron Transport Complex IV