Autoradiographic localization of atrial natriuretic peptide receptor subtypes in rat kidney

The distribution of atrial natriuretic peptide (ANP) clearance receptors in rat kidney was investigated by in vitro autoradiography using des[Gln18,Ser19,Gly20,Leu21,Gly22]-ANP-(4- 23) (C-ANP) and 125I-Tyr0-ANP-(5-25) as relatively specific ligands of this receptor. Alpha-125I-ANP (100 pM) bound reversibly but with high affinity to glomeruli, outer medullary vasa recta bundles, and inner medulla. C-ANP (10 microM) inhibited greater than 60% of this glomerular binding but did not inhibit the binding of alpha-125I-ANP to medullary tissues. Alpha-125I-ANP also bound reversibly to the renal arteries up to the glomerulus. This arterial binding was only partly inhibited by 10 microM C-ANP. In the presence of 10 microM C-ANP, increasing concentrations of alpha-125I-ANP bound to a residue of glomerular sites with apparent dissociation constants of 0.82 +/- 0.16 to 2.73 +/- 1.20 nM at different cortical levels. 125I-Tyr0-ANP-(5-25) bound significantly to glomeruli and intrarenal arteries but not to vasa recta bundles or inner medulla. This glomerular binding also occurred with nanomolar dissociation constants. It was completely inhibited by 1 microM alpha-ANP and 10 microM C-ANP, but not by unrelated peptides such as gastrin. These results suggest that renal ANP clearance receptors are restricted in vivo to the glomeruli and renal arterial system of the rat.