title: I1-imidazoline receptors. Definition, characterization, distribution, and transmembrane signaling.
abstract: Data were presented showing that I1-imidazoline sites show a unique ligand specificity that differs markedly from that of any of the alpha 2-adrenergic subtypes or the I2-imidazoline sites labeled by [3H]idazoxan. On the other hand, the ligand specificity of I1-imidazoline sites is maintained across mammalian species (cow, rat, dog, and human) and between different tissues and cell types. I1-Imidazoline sites can be further distinguished from I2 sites because the latter, unlike I1 sites, were not present in RVLM membranes from bovine brain stem. Furthermore, I1-imidazoline sites were modulated by guanine nucleotides with a specificity appropriate for a receptor coupled to G-protein and were mainly localized to plasma membranes. I1-Imidazoline sites show a unique pattern of distribution between diverse tissues and cell types and appear to be a neuroepithelial marker as well as being present in secretory cells of the pancreatic islets. The widespread distribution of I1-imidazoline sites implies that the functional significance of this putative receptor may have been underestimated. The signaling pathway associated with the I1-imidazoline receptor remains to be fully elucidated, but is likely that activation of phospholipase A2 leading to release of arachidonic acid and subsequent generation of prostaglandins plays a major role.
authors.affiliation: Department of Medicine, Case Western Reserve School of Medicine, Cleveland, Ohio 44106-4982, USA.
authors.forename: P
authors.initials: P
authors.lastname: Ernsberger
authors.forename: M E
authors.initials: ME
authors.lastname: Graves
authors.forename: L M
authors.initials: LM
authors.lastname: Graff
authors.forename: N
authors.initials: N
authors.lastname: Zakieh
authors.forename: P
authors.initials: P
authors.lastname: Nguyen
authors.forename: L A
authors.initials: LA
authors.lastname: Collins
authors.forename: K L
authors.initials: KL
authors.lastname: Westbrooks
authors.forename: G G
authors.initials: GG
authors.lastname: Johnson
mesh_terms: D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D006150:Guanine Nucleotides / Q000378:metabolism; D006801:Humans; D007093:Imidazoles / Q000378:metabolism*; D054755:Imidazoline Receptors; D009474:Neurons / Q000378:metabolism; D011955:Receptors, Drug / Q000378:metabolism*; D015398:Signal Transduction
chemical_list: D006150:Guanine Nucleotides; D007093:Imidazoles; D054755:Imidazoline Receptors; D011955:Receptors, Drug