Alteration of heart uncoupling protein-2 mRNA regulated by sympathetic nerve and triiodothyronine during postnatal period in rats

To provide tissue-specific and developmental characteristics of gene expres sion of rat heart uncoupling protein-2 (UCP2), we investigated developmenta l alterations of UCPs mRNA expression in the heart and brown adipose tissue (BAT), and examined possible up-regulators of heart UCP2 expression using in vitro studies. Heart UCP2 mRNA expression was low during the early postn atal days followed by a rapid and significant increase in the 2nd postnatal week. Heart UCP3 mRNA remained undetectable until the 2nd postnatal week w hen the expression reached a small but significant peak. BAT UCP1 mRNA was abundantly expressed in the neonate, but the expression rapidly decreased t o the adult level. The studies using cultured cardiomyocytes demonstrated t hat both 10(-8) M triiodothyronine and 10(-7) M isoproterenol, but not phen ylephrine, increased UCP2 mRNA expression. These results indicate that the sympathetic nervous system and/or thyroid hormones may be involved in the u p-regulation of heart UCP2 gene expression during postnatal development. Th e increase in postnatal heart UCP2 may provide a key link between the postn atal energy shift and adaptation of rat pups to their novel environment. (C ) 1999 Elsevier Science B.V. All rights reserved.