Intrarenal Localization of Receptors for α-Rat Atrial Natriuretic Polypeptide: An Autoradiographic Study with [125I]-Labeled Ligand Injected in Vivo into the Rat Aorta

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Abstract
We examined intrarenal localization of receptors for α-rat atrial natriuretic polypeptide (α-rANP) by injecting [125I]-labeled ligand in vivo into the rat aorta. We found that the receptors for α-rANP are distributed also on the vasa recta of the outer and inner medulla in addition to the previously reported sites, i.e., the renal arteries, renal pelvis, glomeruli, and inner medullary tissues including collecting tubules. In the vascular bundle of the outer medulla, the majority of grains was preferentially localized on the arterial vasa recta. The electron microscopic autoradiography of the glomerulus showed that the binding sites were mainly localized on the foot process of the podocyte. Since α-rANP injected into the aorta under physiological conditions was bound to the glomerulus and vasa recta in the kidney, the effect of ANP on these binding sites may be important in the mechanism of natriuresis.