NATRIURETIC PEPTIDE RECEPTORS IN THE KIDNEY AND THE VENTRAL AND DORSAL AORTAE OF THE ATLANTIC HAGFISH MYXINE GLUTINOSA (AGNATHA)

The character of natriuretic peptide receptors (NPRs) in the kidney an d aortae of the Atlantic hagfish Myxine glutinosa was determined and c ompared with that of NPRs in hagfish gills, The relationship of hagfis h kidney and aortic NPRs with NPRs from higher vertebrates was also ex amined, Iodinated atrial and C-type natriuretic peptides (NPs) (I-125- ANP, I-125-CNP) were used in tissue section autoradiography, competiti on studies and guanylate cyclase (GC) assays, Rat atrial and porcine C -type NPs (rANP, pCNP) and rat des[Gln(18), Ser(19), Gly(20), Leu,(21) Gly(22)]ANP-(4-23)-NH2 (C-ANF, which binds to the mammalian and teleo st 'clearance' receptor, NPR-C), were used as competing ligands, I-125 .ANP binding sites were observed on both aortae and on the glomeruli, neck segments and archinephric ducts of the kidney, 4.0 nmoll(-1) rANP competed for 50% of I-125-ANP glomerular sites, I-125-CNP did not vis ibly bind to any of the tissues, but 300nmoll(-1) pCNP competed for 50 % of I-125-ANP glomerular sites, C-ANF failed to compete for I-125-ANP sites, rANP and pCNP stimulated cyclic GMP production in kidney membr ane preparations, but C-ANF did not, demonstrating that the hagfish ki dney NPR is GC-linked, This study suggests that a predominant populati on of ANP-like receptors, similar to the mammalian NPR-A, exists in th e myxinoid aortae and kidney tissue, However, no detectable population of a receptor that binds all NPs, such as is present in the hagfish g ill, nor an NPR similar to the NPR-C of higher vertebrates was discove red.