Distribution and characterization of natriuretic peptide receptors in the kidney of the toad, Bufo marinus

The location and characteristics of atrial natriuretic peptide binding site s in the kidney of the toad, Bufo marinus, were determined. Specific I-125- rANP binding sites were observed on glomeruli and blood vessels, but little if any binding was observed over regions corresponding to the renal tubule s. I-125-rANP binding in tissue sections and/or isolated membranes was comp letely displaced in the presence of 1 mu M rat ANP, frog ANP, and porcine C -type natriuretic peptide (membranes only); however, residual binding remai ned after incubation with 1 mu M Of the NPR-C ligand, C-ANF, indicating the presence of two distinct binding sites. Electrophoresis of kidney membrane s cross-linked to I-125-rANP identified specific bands at approximately 70 and 140 kDa which correspond to the monomeric mass of NPR-C and the guanyla te cyclase receptors, respectively. In addition, rat ANP, frog ANP, and por cine CNP stimulated a significant increase in cGMP production rates in memb rane preparations, while C-ANF had no stimulatory effect. Two partial cDNA clones generated using primers based on conserved regions of vertebrate nat riuretic peptide receptors showed high homology to an NPR-C and the natriur etic peptide guanylate cyclase receptors (NPR-GC), respectively. This study provides evidence that the kidney of B. marinus contains both NPR-C and NP R-GC and that the glomerulus is potentially the principal site of ANP regul ation in the kidneys. (C) 1999 Academic Press.