title: Alpha 1-adrenergic stimulation of hamster brown adipocyte respiration.
abstract: Respiration was increased approximately 5-fold with 0.05 microM norepinephrine and to a maximum of 10-fold by 0.30 microM norepinephrine. Prazosin, an alpha-adrenergic blocking agent highly selective for alpha 1-type receptors, partially inhibited the response to norepinephrine (0.05 microM) by 20-25% at a concentration of 0.10-1 microM. In contrast, when the stimulus for respiration was provided by isoproterenol or 3-isobutyl-1-methylxanthine, prazosin was without effect up to a concentration of 10 microM. Yohimbine, an alpha-adrenergic blocking drug preferential for alpha 2-receptors, did not influence norepinephrine-stimulated oxygen uptake. Respiration was increased two- to fourfold by phenylephrine or methoxamine, agents preferential for alpha 1-adrenergic receptors but not at all by clonidine, an agent preferential for alpha 2-adrenergic receptors. The stimulatory effect of phenylephrine on oxygen uptake was fully blocked by prazosin but not propranolol. Removal of extracellular calcium with ethyleneglycol-bis(beta-aminoethylether)-N,N'-tetraacetic acid prevented phenylephrine stimulation of respiration but was without effect when isoproterenol was the stimulus. These results support the participation of alpha 1-adrenergic receptors in control of respiration and are consistent with the possibility that changes in cell calcium are intimately involved in this response.
mesh_terms: D015056:1-Methyl-3-isobutylxanthine / Q000494:pharmacology; D002001:Adipose Tissue, Brown / Q000187:drug effects / Q000378:metabolism*; D000818:Animals; D003000:Clonidine / Q000494:pharmacology; D006224:Cricetinae; D007545:Isoproterenol / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D008647:Mesocricetus; D008729:Methoxamine / Q000494:pharmacology; D009638:Norepinephrine / Q000494:pharmacology*; D010101:Oxygen Consumption / Q000187:drug effects*; D010656:Phenylephrine / Q000494:pharmacology; D011224:Prazosin / Q000494:pharmacology*; D011433:Propranolol / Q000494:pharmacology; D011799:Quinazolines / Q000494:pharmacology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology
chemical_list: D011799:Quinazolines; D011942:Receptors, Adrenergic, alpha; D010656:Phenylephrine; D011433:Propranolol; D008729:Methoxamine; D007545:Isoproterenol; D003000:Clonidine; D015056:1-Methyl-3-isobutylxanthine; D009638:Norepinephrine; D011224:Prazosin