Stimulatory effect of octopamine on β3‐adrenoceptors to lower the uptake of [14C]‐deoxy‐D‐glucose into rat adipocytes in vitro

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Abstract
1. The effect of octopamine on beta 3-adrenoceptors has been studied in isolated adipocytes of Wistar rats using uptake of [14C]-deoxy-D-glucose as the indicator. 2. Octopamine (0.1-1 nmol 1-1) induced a concentration-dependent decrease of [14C]-deoxy-D-glucose uptake into the adipocytes and this inhibition was not influenced by haloperidol at concentrations sufficient to block dopaminergic receptors. 3. Pindolol and propranolol reversed this inhibition of octopamine in a concentration-dependent manner. The effect of octopamine was reduced in the presence of Rp-cyclic AMPS triethylamine, the membrane-permeable antagonist of cyclic AMP (cAMP), indicating the mediation of cAMP in this inhibition. 4. A direct effect of octopamine on beta 3-adrenoceptors was proved using the application of antibodies. In the presence of an antibody for beta 3-adrenoceptors, the actions of octopamine were concentration-dependently reduced in a manner similar to the decrease of BRL37344-induced inhibitions. 5. The same degree of diminished activities for octopamine as that of BRL37344, the well-known specific agonist of beta 3-adrenoceptors, was also obtained in isoprenline-desensitized adipocytes. Insulin-stimulated uptake of [14C]-deoxy-D-glucose into adipocytes was not modified by isoprenaline induced desensitization. 6. These results suggest that octopamine can activate beta 3-adrenoceptors to lower the glucose uptake through an increase of cAMP in rat white adipocytes.