title: Atrial natriuretic factor binding sites in rat area postrema: autoradiographic study.
abstract: The area postrema (AP) is a brain stem circumventricular organ implicated, among other functions, in central cardiovascular (CV) regulation. Competition binding analysis performed by quantitative in vitro autoradiography demonstrated specific, high-affinity (Kd, 0.32 +/- 0.11 nM), low-capacity (Bmax, 57.5 +/- 10.9 fmol/mg protein) atrial natriuretic factor (ANF) binding sites in the AP. C-ANF [des-(Gln116-Gly120)ANF-(Arg102-Cys121)-NH2] and ANF-(Phe106-Ile113)-NH2 (two ligands endowed with selectivity for the ANF-C receptor), as well as C-type natriuretic peptide (CNP), did not compete noticeably at pathophysiological concentrations for 125I-ANF binding. 125I-[Tyr0]CNP bound to the AP to a much lower extent than 125I-ANF. Electron microscopic autoradiography in vivo disclosed that 125I-ANF was preferentially bound to axon, dendrite, and astrocyte plasmalemma. These studies demonstrate that the AP contains natriuretic peptide binding sites with pharmacological characteristics of the ANF-A and ANF-B but not of the ANF-C receptor subtype. In the AP, ANF interacts with those sites resembling ANF-A receptors. Cellular localization of these binding sites may relate to their possible involvement in the centrally mediated salt and water regulation and/or CV effects of circulating ANF.
authors.affiliation: Laboratory of Pathobiology, Clinical Research Institute of Montreal, Quebec, Canada.
authors.forename: E M
authors.initials: EM
authors.lastname: Konrad
authors.forename: G
authors.initials: G
authors.lastname: Thibault
authors.forename: E L
authors.initials: EL
authors.lastname: Schiffrin
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D001345:Autoradiography; D001665:Binding Sites; D001667:Binding, Competitive; D008526:Medulla Oblongata / Q000378:metabolism* / Q000648:ultrastructure; D008854:Microscopy, Electron; D051381:Rats
chemical_list: C472610:atrial natriuretic peptide, rat; D009320:Atrial Natriuretic Factor