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Isoproterenol and selective agonists stimulate similar atypical β-adrenoceptors in rat adipocytes

par Van Liefde, Isabelle;Van Witzenburg, Anne ;Vauquelin, Georges
Référence Biochemical pharmacology, 45, 4, page (974-977)
Publication Publié, 1993

Article révisé par les pairs

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Résumé :

We have demonstrated previously that (-)isoproterenol triggers lipolysis in rat epididymal fat cells by stimulating both classical (β1, β2) and atypical β-adrenoceptors. The contribution of the classical β-adrenoceptors can be blocked by addition of 3 nM CGP12177{di-4-3[(1,1-dimethylethyl)amino]-(2-hydroxylpropoxy)1,3-dihy dro-2H-benzimidazol-2-one hydrochloride}. At higher concentrations, CGP12177 triggers lipolysis also, but by stimulating atypical β-adrenoceptors only. To find out whether (-)isoproterenol and CGP12177 stimulate similar atypical β-adrenoceptors, we compared their interaction with recognised β3-adrenoceptor antagonists: CGP20712 {1-[2-((3-carbamoyl-4-hydroxy)phenoxy)ethylamino]-3-[4-(1-methyl-4-tr ifluoromethyl-2-imidazolyl)phenoxy]propan-2-ol} (βl-selective), ICI118551 [erythro-1-(7-methylindan-4-yloxy)-3-(isopropylamine)-butan-2-ol] (β2-selective) and the stereoisomers as well as the racemic mixture of propanolol (non-β1/β2-subtype selective) and of metoprolol (β1-selective). There was a highly significant relationship (r = 0.93) between the potencies of these antagonists for inhibiting the lipolytic response to (-)isoproterenol (in the absence of classical β-adrenoceptor stimulation) and CGP12177. In both cases, propranolol and metoprolol showed also the same degree of stereoselectivity. These findings suggest that (-)isoproterenol and CGP12177 stimulate the same type and/or form of atypical β-adrenoceptors in rat epididymal adipocytes.