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, uncoupling protein (UCP). Activation and expression of UCP is under control of the sympathetic nervous system acting through beta-adrenergic receptors (AR). In this study we used Siberian hamster brown adipocytes differentiated in vitro to investigate the expression of the fat specific beta(3)-AR. Binding studies using the new labelled beta(3)-adrenergic ligand [H-3]SB 206606 showed a density of beta(3)-AR in brown adipocyte plasma membranes comparable to that measured in vivo. beta(3)-AR mRNA expression was very high in mature brown adipocytes and was started to be expressed during differentiation before UCP mRNA. Its half-life was approximately 50 min. Treatment of cells with non-specific beta adrenergic agonists, specific beta(3)-adrenergic agonists, and dibutyryl cyclic AMP resulted in a marked down regulation of beta(3)-AR mRNA level within several hours.