title: Localisation and characteristics of natriuretic peptide receptors in the gills of the Atlantic hagfish Myxine glutinosa (Agnatha).
abstract: Specific binding of iodinated natriuretic peptides 125I-ANP and 125I-CNP was examined in the gill of the Atlantic hagfish Myxine glutinosa by tissue section autoradiography, saturation and competition analysis of binding to membrane preparations, affinity cross-linking, followed by SDS-PAGE and guanylate cyclase assays. Autoradiographs showed specific, saturable binding on the respiratory lamellar epithelium. In vitro analysis of the binding sites demonstrated that 125I-ANP bound to two receptor sites with the same affinity (Kd = 15.4 +/- 1.6 pmol l-1; Bmax = 45.9 +/- 3.0 fmol mg-1 protein). 125I-CNP bound to high- and low-affinity receptor sites; variables for the high-affinity site (Kd = 12.9 +/- 4.7 pmol l-1; Bmax = 23.4 +/- 6.5 fmol mg-1 protein) did not differ from those for the 125I-ANP sites. The low-affinity site had an apparent Kd and Bmax of 380 +/- 80 pmol l-1 and 120 +/- 21 fmol mg-1 protein, respectively. All receptors had an apparent molecular mass of approximately 150 kDa, with no indication of a mammalian type NPR-C at a lower apparent molecular mass. 1 nmol l-1 unlabelled rANP and 20 and 30 nmol l-1 unlabelled pCNP and C-ANF, respectively, competed for 50% of 125I-ANP sites. 0.1 nmol l-1 rANP and pCNP and 8 nmol l-1 C-ANF competitively inhibited 50% of 125I-CNP binding. Both rANP and pCNP stimulated cyclic GMP production, although rANP was a more potent stimulator than was pCNP. C-ANF did not stimulate cyclic GMP production. These data suggest the existence of an ANP guanylate-cyclase-linked receptor similar to the mammalian NPR-A and an ANP/CNP receptor that may be similar to, although not structurally homologous with, the mammalian NPR-C clearance receptor.
authors.affiliation: Department of Zoology, University of Florida, Gainesville 32611.
authors.forename: T
authors.initials: T
authors.lastname: Toop
authors.forename: J A
authors.initials: JA
authors.lastname: Donald
authors.forename: D H
authors.initials: DH
authors.lastname: Evans
mesh_terms: D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D001345:Autoradiography; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D004591:Electrophoresis, Polyacrylamide Gel; D005880:Gills / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000378:metabolism*; D006196:Hagfishes; D007457:Iodine Radioisotopes; D008970:Molecular Weight; D020098:Natriuretic Peptide, C-Type; D011506:Proteins / Q000378:metabolism; D017461:Receptors, Atrial Natriuretic Factor / Q000378:metabolism*
chemical_list: D007457:Iodine Radioisotopes; D011506:Proteins; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor; C073616:atrial natriuretic factor receptor C