Characterization of receptors for the atrial natriuretic factor in rat renal microvessels.
OBJECTIVE
To characterize [125I]-atrial natriuretic factor [ANF-(99-126)] binding sites in the renal preglomerular microvasculature of Sprague-Dawley rats.


METHODS
Renal preglomerular microvessels were isolated by infusion of a magnetized iron oxide solution into the renal arteries and detachment from non-vascular tissue by a magnetic field. In order to characterize [125I]-ANF-(99-126) binding sites, saturation and competitive binding experiments were performed. To evaluate the proportions of ANF receptor subtypes (ANF-R1, ANF-R2), competition curves were charted in the presence of 10(-6) mol/l C-ANF-(4-23), a specific ligand of ANF-R2 (ANP-C).


RESULTS
[125I]-ANF binding to vascular membranes was saturable and of high affinity. Equilibrium saturation binding curves suggested the presence of one group of high-affinity receptors [equilibrium dissociation constant (Kd) 22 +/- 6 pmol/l; binding capacity (Bmax) 118 +/- 6 fmol/mg protein]. In competitive inhibition experiments, no significant differences were found in binding capacity between experiments performed either in the presence or in the absence of an excess (1 mumol/l) of C-ANF (94 +/- 27 versus 151 +/- 35 fmol/mg protein, respectively), suggesting that most receptors in the renal vasculature are of the subtype ANF-R1. Incubation of renal microvessels with ANF-(99-126) stimulated cyclic GMP production in a dose-related manner. In parallel studies, the proportion of ANF-R1 (ANP-A, -B) and ANF-R2 (ANP-C) receptors in glomeruli, calculated from competitive inhibition experiments, was 86 +/- 2 and 14 +/- 2%, respectively (P < 0.005).


CONCLUSIONS
These results indicate that rat renal preglomerular microvessels contain a high proportion of guanylate cyclase-coupled ANF-R1 (ANP-A, -B) and a low density of ANF-R2 (ANP-C) receptors. This difference in the proportion of ANF receptor subtypes, compared to that reported in glomeruli and other vascular beds, may have physiological significance.
De León
H
H
Laboratory of Experimental Hypertension and Vasoactive Peptides, Clinical Research Institute of Montreal, Quebec, Canada.
Gauquelin
G
G
Thibault
G
G
Garcia
R
R
D000818:Animals; D009320:Atrial Natriuretic Factor / Q000378:metabolism; D001667:Binding, Competitive; D006152:Cyclic GMP / Q000096:biosynthesis; D007668:Kidney / Q000098:blood supply*; D008833:Microcirculation / Q000737:chemistry; D010446:Peptide Fragments / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D017461:Receptors, Atrial Natriuretic Factor / Q000032:analysis*
D010446:Peptide Fragments; C472610:atrial natriuretic peptide, rat; D009320:Atrial Natriuretic Factor; D017461:Receptors, Atrial Natriuretic Factor; D006152:Cyclic GMP