title: Vascular atrial natriuretic factor receptor subtypes are not independently regulated by atrial peptides.
abstract: The regulation of the atrial natriuretic factor (ANF) receptor system in cultured rat vascular smooth muscle cells (RVSMC) was examined following long term pretreatment of these cells with rANF99-126 or with any one of a series of truncated and ring-deleted analogs. The latter analogs are reported to bind selectively the ANF-C or clearance receptor. Initial competition binding studies revealed that all analogs examined showed comparable apparent receptor binding affinities (Ki values did not differ by more than 10-fold). In contrast, the extent of interaction of the ANF analogs with the receptor pool coupled to particulate guanylate cyclase (the ANF-B receptor) was much more variable, with some ligands failing to stimulate cGMP production or particulate guanylate cyclase over the concentrations tested. Pretreatment of cells for 24 h with rANF99-126 or any of the truncated analogs that interact with the ANF-B receptor caused a dose- and time-dependent decrease in the number of ANF binding sites (99% of which are uncoupled in RVSMC) without any change in affinity. Examination of the binding activity following pretreatment of the cells with ANF suggested that the observed reduction in 125I-rANF99-126 binding capacity was not because of the retention of the peptide on its receptor. Furthermore, this down-regulation was associated with desensitization of particulate guanylate cyclase resulting in a decreased responsiveness of intracellular cGMP accumulation to ANF. In contrast, however, analogs selective for the ANF-C receptor pool failed to cause down-regulation or desensitization. These findings suggest that ANF-C receptors in RVSMC are not independently down-regulated by selective ligands but that nonselective analogs that down-regulate and desensitize the ANF-B receptor system can by some cooperative mechanism reduce the size of the predominant ANF-C receptor pool in these cells.
authors.affiliation: Department of Pharmacology, University College Dublin, Belfield, Ireland.
authors.forename: P A
authors.initials: PA
authors.lastname: Cahill
authors.forename: E M
authors.initials: EM
authors.lastname: Redmond
authors.forename: A K
authors.initials: AK
authors.lastname: Keenan
mesh_terms: D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D009320:Atrial Natriuretic Factor / Q000737:chemistry / Q000378:metabolism*; D001667:Binding, Competitive; D006152:Cyclic GMP / Q000378:metabolism; D015536:Down-Regulation; D066298:In Vitro Techniques; D008969:Molecular Sequence Data; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D010446:Peptide Fragments / Q000737:chemistry / Q000378:metabolism; D051381:Rats; D017461:Receptors, Atrial Natriuretic Factor; D011956:Receptors, Cell Surface / Q000378:metabolism*; D013329:Structure-Activity Relationship
chemical_list: D000345:Affinity Labels; D010446:Peptide Fragments; D011956:Receptors, Cell Surface; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP