Uncoupling protein1 mRNA, mitochondrial GTP-binding, and T-4 5 '-deiodinase of brown adipose tissue in euthermic Daurian ground squirrel during cold exposure

Regulation of thermogenic activity and uncoupling protein1 (UCP1) expressio n in brown adipose tissue (BAT) were studied in euthermic Daurian ground sq uirrel after acute and chronic cold exposure at 4 degreesC. The UCP1 concen tration was indirectly determined by titration with its specific ligand [H- 3]-labeled GTP, and Ucp1 mRNA was detected by using a [P-32]-labeled antise nse oligonucleotide probe. Both acute and chronic cold exposure stimulated up-regulation of Ucp1 mRNA, Although UCP1 concentration is not significantl y increased after 24 h of cold exposure, it is markedly elevated by 75% in squirrels after 4-week cold adaptation compared with controls raised at 22 degreesC. Changes in T-4 5'-deiodinase activity were closely associated wit h variations of Ucp1 mRNA level. Ucp1 gene expression is significantly affe cted by cold exposure in BAT from euthermic Daurian ground squirrels. In ad dition, the activation of T-4 5'-deiodinase may be an important regulatory factor in cold-induced Ucp1 expression. (C) 2001 Elsevier Science Inc. All rights reserved.