title: Adrenoceptor of the alpha 2-subtype mediating inhibition of the human fat cell adenylate cyclase.
abstract: In an attempt to characterize the adenylate cyclase-coupled alpha-adrenoceptors of human fat cells the effects of various alpha-adrenergic agonists and antagonists were examined in the presence of 0.05 mmol/l of propranolol. The order of agonist potencies with respect to alpha-adrenergic inhibition was (-)-adrenaline greater than alpha-methyl-(-)-noradrenaline greater than (-)-phenylephrine with half-maximal inhibition occurring at 2 mumol/l of (-)-adrenaline and 7 mumol/l of alpha-methyl-(-)-noradrenaline respectively. The inhibition of adenylate cyclase induced by 0.05 mmol/l of (-)-adrenaline was reversed by the alpha-blocking agents yohimbine and prazosin, with the alpha 2-site-directed antagonist yohimbine being more than 100-times more potent than prazosin which is more active at alpha 1-sites. The results show that the cyclase-coupled alpha-adrenoceptors of human fat cells, which probably represent the physiologically relevant target of antilipolytic catecholamine effects, display characteristic features of the alpha 2-adrenoceptor subtype.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism*; D000273:Adipose Tissue / Q000166:cytology / Q000201:enzymology*; D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology; D002395:Catecholamines / Q000494:pharmacology; D006801:Humans; D011941:Receptors, Adrenergic / Q000502:physiology*; D011942:Receptors, Adrenergic, alpha / Q000502:physiology*
chemical_list: D000316:Adrenergic alpha-Agonists; D000317:Adrenergic alpha-Antagonists; D002395:Catecholamines; D011941:Receptors, Adrenergic; D011942:Receptors, Adrenergic, alpha; D000262:Adenylyl Cyclases