In vitro autoradiographic localization of ANP receptors in rat kidney and adrenal gland.

The radioligand 125I-ANP-(99-126) was used to map receptors for atrial natriuretic peptide (ANP) in the rat kidney and adrenal gland using in vitro autoradiography and computerized densitometry. In the kidney a very high density of receptors was found overlying glomeruli; these sites had a binding affinity constant of 0.48 +/- 0.06 X 10(-9) M-1 and a site concentration 818 +/- 108 fmol X mg protein-1. A moderate density of receptors was seen in the inner renal medulla; these sites had a binding constant of 0.9 +/- 0.2 X 10(9) M-1 and a receptor concentration of 204 +/- 44 fmol X mg protein-1, and moderate receptor density was also seen in the inner stripe of the outer medulla overlying vasa recta bundles. Diffuse low-density binding was also detected in the outer cortex. In all cases these patterns were abolished by 1 micron ANP-(101-126) or 1 microM atriopeptin III but not by a range of unrelated peptides. In the adrenal, a high density of binding was found overlying the zona glomerulosa, whereas a moderate density occurred in the zona fasciculata. Binding was not detected in the adrenal medulla. These results provide evidence for several classes of ANP receptor distribution in kidney and adrenal and suggest multiple roles of the peptide in fluid and electrolyte homeostasis.