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Updated: Aug 3, 2026

Differentiation and Imaging of Brown Adipocytes from the Stromal Vascular Fraction of Interscapular Adipose Tissue from Newborn Mice
Published on: February 3, 2023
[Adenylate cyclase response to beta-adrenergic agonists in heart and brown adipose tissue]
G Garruti1, G De Pergola, M Cignarelli
1Clinica Medica III, Università di Bari.
Abstract:
Some sympathomimetic compounds (i.e. BRL37344) increase brown adipose tissue (BAT) thermogenesis with minimal cardiac effects. They act through an "atypical" beta-adrenergic receptor (beta-AR). Since beta-AR responses involve Adenylate Cyclase (AC) activation, we investigate the AC answer to isoproterenol and BRL37344 in rat plasmamembranes of heart (beta 1-ARs) and BAT (atypical beta-ARs). AC dose-response curves were obtained by incubating membrane fractions with different concentrations of isoproterenol and BRL37344 (1 nM-100 microM) at 25 degrees C for 15 min. In our study BRL37344 is 40-times more potent than isoproterenol in stimulating AC activity of BAT (EC50s: BRL37344 = 0.02 microM, isoproterenol = 0.7 microM). Furthermore it is more potent in stimulating BAT AC than heart AC (BRL37344 EC50 ratio heart/BAT = 38). However on BAT membranes, BRL37344 intrinsic sympathomimetic activity (ISA) vs. Isoproterenol is 0.87. Since isoproterenol and BRL37344 show a similar ISA for BAT respiration and lipolysis, we may argue that AC maximal activity is not required for maximal lipolytic and thermogenic responses.
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