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.
Laboratory of Experimental Hypertension and Vasoactive Peptides, Clinical Research Institute of Montreal, Quebec, Canada.
H
H
De León
G
G
Gauquelin
G
G
Thibault
R
R
Garcia
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