title: Identification of alpha 2-adrenergic receptor sites in human retinoblastoma (Y-79) and neuroblastoma (SH-SY5Y) cells.
abstract: The existence of specific alpha 2-adrenergic receptor sites has been shown in human retinoblastoma (Y-79) and neuroblastoma (SH-SH5Y) cells using direct radioligand binding. [3H]Rauwolscine, a selective alpha 2-adrenergic receptor antagonist, exhibited high affinity, saturable binding to both Y-79 and SH-SY5Y cell membranes. The binding of alpha 1 specific antagonist, [3H]Prazocine, was not detectable in either cell type. Competition studies with antagonists yielded pharmacological characteristics typical of alpha 2-adrenergic receptors: rauwolscine greater than yohimbine greater than phentolamine greater than prazocine. Based on the affinity constants of prazocine and oxymetazoline, it appears that Y-79 cells contain alpha 2A receptor, whereas SH-SY5Y cells probably represent a mixture of alpha 2A and alpha 2B receptors. alpha 2-agonists clonidine and (-)epinephrine inhibition curves yielded high and low affinity states of the receptor in SH-SY5Y cells. Gpp(NH)p and sodium ions reduced the proportion of high affinity sites of alpha 2 receptors. These two neuronal cell lines of human origin would prove useful in elucidating the action and regulation of human alpha 2-adrenergic receptors and their interaction with other receptor systems.
authors.affiliation: Department of Psychiatry, McMaster University, Hamilton, Ontario, Canada.
authors.forename: S M
authors.initials: SM
authors.lastname: Kazmi
authors.forename: R K
authors.initials: RK
authors.lastname: Mishra
mesh_terms: D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D003000:Clonidine / Q000494:pharmacology; D004837:Epinephrine / Q000494:pharmacology; D006165:Guanylyl Imidodiphosphate / Q000494:pharmacology; D006801:Humans; D009447:Neuroblastoma / Q000378:metabolism*; D010646:Phentolamine / Q000378:metabolism; D011224:Prazosin / Q000378:metabolism; D011942:Receptors, Adrenergic, alpha / Q000187:drug effects / Q000378:metabolism*; D012175:Retinoblastoma / Q000378:metabolism*; D012964:Sodium / Q000494:pharmacology; D014316:Tritium; D014407:Tumor Cells, Cultured; D015016:Yohimbine / Q000378:metabolism
chemical_list: D011942:Receptors, Adrenergic, alpha; D014316:Tritium; D015016:Yohimbine; D006165:Guanylyl Imidodiphosphate; D012964:Sodium; D003000:Clonidine; D011224:Prazosin; D004837:Epinephrine; D010646:Phentolamine