title: Alpha2-adrenoceptor agonists stimulate high-affinity GTPase activity in a receptor subtype-selective manner.
abstract: Transfected Chinese hamster ovary cells expressing human alpha2A-, alpha2B- and alpha2C-adrenoceptor subtypes were used to monitor alpha2-adrenoceptor-stimulated GTP hydrolysis. Incubation with 100 microM (-)-adrenaline resulted in stimulation of pertussis toxin-sensitive GTPase by 380% after activation of the alpha2A-subtype, by 320% after activation of the alpha2B-subtype and by 110% after activation of the alpha2C-subtype. The agonists dexmedetomidine, UK14,304 (5-bromo-6-[2-imidazoline-2-ylamino]quinoxaline) and oxymetazoline showed subtype-dependent efficacy. Dexmedetomidine was a full agonist at the alpha2B-subtype and a partial agonist at the alpha2A- and the alpha2C-subtypes. UK14,304 was a full agonist at the alpha2A-subtype and a partial agonist at the other two. Oxymetazoline showed strong partial agonism at the alpha2B-subtype (63% of adrenaline), but did not significantly activate the alpha2A- and the alpha2C-subtypes. These results agreed with cAMP accumulation experiments carried out with cell lines endogenously expressing the alpha2A-subtype (human erythroleukemia, HEL) or the alpha2B-subtype (neuroblastoma-glioma, NG108-15). The GTPase assay may thus provide a valuable tool for the identification of subtype-selective alpha2-adrenoceptor agonists.
authors.affiliation: Department of Pharmacology and Clinical Pharmacology, University of Turku, Finland.
authors.forename: C C
authors.initials: CC
authors.lastname: Jansson
authors.forename: K
authors.initials: K
authors.lastname: Pohjanoksa
authors.forename: J
authors.initials: J
authors.lastname: Lang
authors.forename: S
authors.initials: S
authors.lastname: Wurster
authors.forename: J M
authors.initials: JM
authors.lastname: Savola
authors.forename: M
authors.initials: M
authors.lastname: Scheinin
mesh_terms: D058647:Adrenergic alpha-2 Receptor Agonists; D000818:Animals; D016466:CHO Cells; D002462:Cell Membrane / Q000201:enzymology; D006224:Cricetinae; D000242:Cyclic AMP / Q000096:biosynthesis; D004837:Epinephrine / Q000494:pharmacology; D020558:GTP Phosphohydrolases / Q000378:metabolism*; D006160:Guanosine Triphosphate / Q000378:metabolism; D006801:Humans; D006868:Hydrolysis; D037342:Pertussis Toxin; D018341:Receptors, Adrenergic, alpha-2 / Q000145:classification; D010566:Virulence Factors, Bordetella / Q000494:pharmacology
chemical_list: D058647:Adrenergic alpha-2 Receptor Agonists; D018341:Receptors, Adrenergic, alpha-2; D010566:Virulence Factors, Bordetella; D006160:Guanosine Triphosphate; D000242:Cyclic AMP; D037342:Pertussis Toxin; D020558:GTP Phosphohydrolases; D004837:Epinephrine