UNCOUPLING PROTEIN MESSENGER-RNA, MITOCHONDRIAL GTP-BINDING, AND T-4 5'-DEIODINASE ACTIVITY OF BROWN ADIPOSE-TISSUE IN DAURIAN GROUND-SQUIRREL DURING HIBERNATION AND AROUSAL

The mRNA level of uncoupling protein (UCP) specific for brown adipose tissue (BAT) in Daurian ground squirrel, was detected by using a [P-32 ]-labeled oligonucleotide probe. The UCP concentration in mitochondria was indirectly determined by titration with its specific ligand [H-3] -labeled GTP. Type II T-4 5'-deiodinase of BAT was assayed concomitant ly. We found two species of mRNA for UCP with lengths of about 1.9 and 1.5 kb, respectively, both occurring in almost the same concentration . UCP mRNA content was elevated significantly during hibernation, but the UCP concentration did not change compared with that of nonhibernat ing controls kept at room temperature. When hibernating squirrels were aroused, the UCP mRNA remained at the elevated level as during hibern ation, but the UCP concentration increased in comparison with that of nonhibernating controls or during hibernating. Changes in T-4 5'-deiod inase activity in BAT were similar to the variations of the UCP mRNA l evel. These results suggest that the activation of T-4 5'-deiodinase i n BAT may be an important factor for the up-regulation and maintenance of UCP mRNA content needed for the synthesis of sufficient UCP to acq uire the thermogenic capacity for arousal from hibernation. (C) 1998 E lsevier Science Inc. All rights reserved.