title: beta-Adrenergic receptors in pediatric tumors: uncoupled beta 1-adrenergic receptor in Ewing's sarcoma.
abstract: beta-Adrenergic receptors were demonstrated in membrane preparations from 6 human Ewing's sarcomas and compared to those from 46 other pediatric cancers with the use of the beta-adrenergic antagonist (-)-(3H)dihydroalprenolol [(-)[3H]DHA]. In contrast to the high numbers of receptor sites found in Ewing's sarcomas (55-640 fmol x mg-1 protein; dissociation constant Kd, 1-2 nM), other childhood cancers (neuroblastoma, rhabdomyosarcoma, brain tumors, lymphoma, osteosarcoma, hepatoblastoma, yolk sac, and Wilms' tumor) contained in general fewer beta-adrenergic receptor sites. Characteristics of (-)-[3H]DHA binding were therefore more fully characterized in the Ewing's tumors. Competition of (-)-[3H]DHA binding by classical catecholamine agonists, as well as by subtype selective agents metoprolol and zinterol, demonstrated the presence of a homogeneous population of beta 1-adrenergic sites in several Ewing's tumors. Adenylate cyclase activity in all Ewing's sarcomas was enhanced by GTP and NaF. However, in spite of high numbers of beta-adrenergic receptors, (-)-isoproterenol was not very effective in the activation of adenylate cyclase activity in several of the Ewing's tumors tested. Neither guanyl-5'-yl-imidophosphate nor GTP altered agonist potency for the receptor site in these catecholamine-insensitive tumors. Hill coefficients obtained from the competition experiments with (-)-isoproterenol (in the presence or absence of guanine nucleotide) were approximately 1.0. These uncoupled receptors were resistant to N-ethylmaleimide denaturation and were densensitized only 50% during culture in the presence of (-)-isoproterenol. Thus Ewing's sarcomas are relatively rich in beta-adrenergic sites, and several tumors appear to have a coupling lesion involving guanine nucleotide-dependent regulatory protein interaction with beta-adrenergic receptors and adenylate cyclase, similar in phenotype to that described in the (unc) variant of S49 mouse lymphoma.
mesh_terms: D000262:Adenylyl Cyclases / Q000378:metabolism; D000319:Adrenergic beta-Antagonists; D000818:Animals; D001667:Binding, Competitive; D001859:Bone Neoplasms / Q000378:metabolism*; D002460:Cell Line; D002648:Child; D004082:Dihydroalprenolol / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D006801:Humans; D008790:Metoprolol / Q000494:pharmacology; D051379:Mice; D008819:Mice, Nude; D009447:Neuroblastoma; D012516:Osteosarcoma; D011943:Receptors, Adrenergic, beta / Q000032:analysis*; D012512:Sarcoma, Ewing / Q000378:metabolism*
chemical_list: D000319:Adrenergic beta-Antagonists; D004983:Ethanolamines; D011943:Receptors, Adrenergic, beta; D004082:Dihydroalprenolol; C002904:zinterol; D000262:Adenylyl Cyclases; D008790:Metoprolol