title: Natriuretic peptide binding sites in the gills of the pouched lamprey Geotria australis.
abstract: Iodinated atrial natriuretic peptide (ANP) binding sites were examined in the gills and ventral aorta of the adult upstream-migrating lamprey Geotria australis using tissue section autoradiography, in vitro competition analysis and affinity cross-linking, while guanylate cyclase assays were performed on gill membranes of both adult and juvenile lampreys. A partial natriuretic peptide (NP) receptor sequence was amplified using reverse transcription/polymerase chain reaction (RT-PCR). The results indicated that there was specific NP binding to the aortic endothelium and to pillar cell regions in the axial plate and secondary lamellae. In competition studies, 50 % of NP binding was abolished by 4 nmol l-1 rat ANP, 35 nmol l-1 porcine C-type NP (CNP) and 45 nmol l-1 C-ANF (a truncated ANP). Affinity cross-linking followed by SDS-PAGE demonstrated two binding sites at 205 and 65 kDa under non-reducing conditions and at 85 and 65 kDa under reducing conditions. Guanylate cyclase assays demonstrated that, while no NP-stimulated GC activity occurred in adult lampreys, NP-stimulated enhancement of cyclic GMP accumulation was found in juveniles in fresh water and more particularly in salt water. RT-PCR amplified a 471 base pair fragment with 68 % amino acid sequence homology to the eel natriuretic peptide receptor D (NPR-D). This study suggests that NP binding sites in the adult gill and aorta are of an NPR-C/D type, whereas an additional GC-coupled site exists in juveniles.
authors.affiliation: School of Biological and Chemical Sciences, Deakin University, Geelong, Victoria 3228, Australia. ttoop@deakin.edu.au
authors.forename: T
authors.initials: T
authors.lastname: Toop
authors.forename: D
authors.initials: D
authors.lastname: Grozdanovski
authors.forename: I C
authors.initials: IC
authors.lastname: Potter
mesh_terms: D000345:Affinity Labels; D000595:Amino Acid Sequence; D000818:Animals; D001011:Aorta / Q000378:metabolism; D009320:Atrial Natriuretic Factor / Q000378:metabolism*; D001483:Base Sequence; D001665:Binding Sites; D001667:Binding, Competitive; D002462:Cell Membrane / Q000378:metabolism; D003001:Cloning, Molecular; D003432:Cross-Linking Reagents; D005880:Gills / Q000378:metabolism*; D006162:Guanylate Cyclase / Q000378:metabolism; D007457:Iodine Radioisotopes; D007798:Lampreys; D008969:Molecular Sequence Data; D020098:Natriuretic Peptide, C-Type; D016133:Polymerase Chain Reaction; D011506:Proteins / Q000378:metabolism; D017461:Receptors, Atrial Natriuretic Factor / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D014158:Transcription, Genetic
chemical_list: D000345:Affinity Labels; D003432:Cross-Linking Reagents; D007457:Iodine Radioisotopes; D011506:Proteins; D020098:Natriuretic Peptide, C-Type; D009320:Atrial Natriuretic Factor; D006162:Guanylate Cyclase; D017461:Receptors, Atrial Natriuretic Factor