Specific receptor binding of atrial natriuretic peptide to rat renal cortex

Radiolabeled receptor assay (RRA) of atrial natriuretic peptide (ANP) was studied in rat kidney membranes. Binding of [125I]-ANP to membrane preparations of rat whole kidney was saturated and show a high affinity (Kd = 0.51 nM). Furthermore, renal cortex membrane had a higher affinity for ANP binding site (Kd = 0.26 nM) than renal medulla membrane (Kd greater than 100 nM). This high affinity ANP receptor site in renal cortex membrane indicated that ANP controlled the balance of water and sodium excretion due to this receptor site in the kidney.