Renal action of atrial natriuretic peptide

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Interactions between atrial natriuretic peptide(ANP) and the kidney were examined by various approaches including autoradiography, receptor binding study, clearance study, in vitro microperfusion of renal tubules, and others. The following 5 major results were obtained: (1) By sutoradiography, we demonstrated that receptors for ANP were distributed in the glomeruli (foot processes of epithelial cells), vascular bundles and inner medullary collecting tubules. By solubilizing ANP-receptors labeled by photoaffinity method, we found that molecular size of the receptors in the kidney is 65 kD wherease the aorta and the adrenal grand contain two kinds of receptors having different molecular size, 65 kD and 140 kD. (2) The structure-activity relationship, examined by using -hANP analogs, showed that amino acids in N-termainus, amino acid at 12th position and ring structure are essential for physiological effects. (3) Intrarenal arterial administration of ANP in combination with acetyl choline or secretin suggested that effects of ANP are mediated in part by its renal vascular action. (4) In vitro microperfusion of isolated renal tubules failed to demonstrate any effects on NaCl and water transport in segments of Henle's loop and inner medullary collecting tubule. (5) Degradation of ANP, inhibitable with phospholamidone, was localized to both the glomeruli and the proximal tubules.