Receptors for natriuretic peptides in a human cortical collecting duct cell line

Receptors for natriuretic peptides in a human cortical collecting duct cell line. The aim of the present study was to analyze the expression of natriuretic peptide receptors in human collecting duct, by using a newly established SV40 cell line (HCD). ANP and C-type natriuretic peptide (CNP) induced a concentration-dependent increase in cGMP suggesting the presence of type-B (NPR-A) and type-B (NPR-B) receptors, respectively. Threshold concentrations were 1pM and 1 nM, respectively, and stimulated over basal cGMP ratios were 500 and 160 at 0.1 µ M ANP and CNP. The urodilatin concentration-response curve was similar to that of ANP. [ 125 I]-ANP bound specifically to HCD cells in a time-dependent fashion, reaching a plateau-phase between one and two hours at 4°C. Equilibrium saturation binding curves suggested a single group of receptor sites (Kd = 421 ± 55 pM, B max = 49.2 ± 8.8 fmol/mg protein, Hill coefficient=1.44 ± 0.1, N = 6). Binding of [ 125 I]-ANP was not displaced by CNP or by C-ANP (4–23), a specific ligand of clearance receptors (NPR-C), and thus occurred mainly via NPR-A. Neither Northern blot analysis nor RT-PCR could detect NPR-C mRNA, although the latter was clearly identified in control human glomerular visceral epithelial cells. In contrast, PCR products with the expected lengths were obtained for NPR-A and NPR-B. In conclusion, HCD cells express both NPR-A and NPR-B, as demonstrated by mRNA and cGMP production studies, but fail to produce NPR-C. This suggests that the human cortical collecting duct is a target for ANP, CNP and urodilatin.