Natriuretic peptide receptors, NPR-A and NPR-B, in cultured rabbit retinalpigment epithelium cells

We tried to detect natriuretic peptide (NP) receptor (NPR-A and NPR-B) mRNA s in cultured rabbit retinal pigment epithelium (RPE) cells and examined th e regulation of their expression in relation to subretinal fluid absorption or RPE cell proliferation. RPE cells from 2-4 passages were grown to confl uence on microporous membranes and analyzed for levels of expression of rec eptor mRNAs by quantitative RT-PCR and Northern blotting. The expression of NPR-B mRNA was approximately tenfold higher than that of NPR-A mRNA. The e xpression of NPR-A mRNA was not affected by treatments that may change subr etinal fluid transport, while that of NPR-B mRNA was inhibited by transmitt ers involved in light- and dark-adaptation such as dopamine and melatonin. Expression of NPR-B mRNA was also suppressed by platelet-derived growth fac tor and transforming growth factor-beta. Furthermore, atrial natriuretic pe ptide (ANP) and C-type natriuretic peptide (CNP), ligands for NPR-A and B, respectively, inhibited the proliferation of RPE cells, as analyzed by inco rporation of [H-3]thymidine. These findings suggest that ANP may be involve d in constitutive absorption of subretinal fluid and that NPs form an impor tant regulatory system of proliferation in RPE cells.