CONTROL OF BETA(3)-ADRENERGIC RECEPTOR GENE-EXPRESSION IN BROWN ADIPOCYTES IN CULTURE

Brown adipose tissue is a mammalian thermogenic tissue. its ability to dissipate energy as heat is due to a unique mitochondrial protein, un coupling protein (UCP). Activation and expression of UCP is under cont rol of the sympathetic nervous system acting through beta-adrenergic r eceptors (AR). In this study we used Siberian hamster brown adipocytes differentiated in vitro to investigate the expression of the fat spec ific beta(3)-AR. Binding studies using the new labelled beta(3)-adrene rgic ligand [H-3]SB 206606 showed a density of beta(3)-AR in brown adi pocyte plasma membranes comparable to that measured in vivo. beta(3)-A R mRNA expression was very high in mature brown adipocytes and was sta rted to be expressed during differentiation before UCP mRNA. Its half- life was approximately 50 min. Treatment of cells with non-specific be ta adrenergic agonists, specific beta(3)-adrenergic agonists, and dibu tyryl cyclic AMP resulted in a marked down regulation of beta(3)-AR mR NA level within several hours.