AJP - Renal Physiology, Vol 250, Issue 2 210-F216, Copyright © 1986 by American Physiological Society
Localization of binding sites for alpha-rat atrial natriuretic polypeptide in rat kidney
C. Koseki, Y. Hayashi, S. Torikai, M. Furuya, N. Ohnuma and M. Imai
To determine the intrarenal localization of receptors for atrial
natriuretic polypeptide (ANP) in the rat, we performed autoradiography and
binding assay by using 125I-labeled alpha-rat ANP (alpha-rANP).
Autoradiography at the slice and microscopic level in the kidney and
binding assay in isolated glomeruli demonstrated that receptors in the
renal cortex were distributed mainly in glomeruli. Although dense silver
grains were distributed diffusely both in inner medulla and outer stripe of
outer medulla, a marked displacement of the grains was observed only in the
inner medulla. Autoradiography at the microscopic level also showed that
silver grains were distributed in the renal artery, renal pelvis, and inner
medullary collecting tubule (IMCT) prepared by the microdissection method,
but not in the arcuate artery, interlobular artery, and afferent or
efferent arterioles. Specific binding was demonstrated in the isolated
glomeruli and the preparation was rich in fragments of IMCT. Apparent
binding affinity (Kd) and receptor density (R) for 125I-labeled alpha-rANP
in isolated glomeruli and IMCT were Kd = 3.2 and 21 X 10(-9) M, and R = 320
and 420 fmol/mg protein, respectively. These observations suggest that
alpha-rANP has a physiological action on glomeruli and possibly on the
inner medullary collecting tubules in addition to the renal artery.
