Respective degree of expression of β1, β2‐ and β3‐adrenoceptors in human brown and white adipose tissues

Open Access
Publisher Website
Google Scholar
Abstract
1 The possible existence of a β3-adrenoceptor in human brown and white adipose tissues was investigated by mRNA expression and binding studies. 2 The relative amounts of β1-, β2- and β3-adrenoceptor mRNA, as determined by total RNA Northern blot analysis in newborn brown adipose tissue, were 28, 63 and 9% respectively of the total β-adrenoceptor mRNA. 3 The β1/β2-adrenoceptors of human brown adipose tissue plasma membranes were characterized using [3H]-CGP 12177 as a ligand. Their Kd and Bmax values were 1.9 nM and 156 fmol mg−1 of membrane proteins, respectively. The β3-adrenoceptor was characterized by use of the new specific radioligand [3H]-SB 206606. The binding of this ligand was stereospecifically displaced by the active R, R- or the inactive S, S-enantiomer of BRL 37344 up to a concentration of about 10 μm. The Kd and Bmax values of the brown adipose tissue membrane β3-adrenoceptors were 87 nM and 167 fmol mg−1 of proteins, respectively. A low affinity [3H]-CGP 12177 binding site population was also detected in these membranes. 4 In human omental white adipose tissue, no β3-adrenoceptor mRNA could be detected in total RNA Northern blots and the β1- and β2-adrenoceptor mRNAs represented 9 and 91%, respectively of the total β-adrenoceptor mRNA, and no specific binding of [3H]-SB 206606 could be measured.