Natriuretic peptides and their receptors in human neural retina and retinal pigment epithelium.

Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) play a role in transepithelial fluid movement in the kidney and at the blood-aqueous barrier. We sought a similar natriuretic peptide-mediated regulatory system at the level of the blood-retinal barrier by investigating human neural retina and retinal pigment epithelium for the presence of ANP, BNP and their receptors. ANP and BNP binding to receptors could be demonstrated autoradiographically in all layers of the retina inclusive of the retinal pigment epithelium. Competitive preincubation with unlabeled peptides blocked the binding of the respective radioactive peptide. ANP and BNP could also be demonstrated immunohistochemically in both the neural retina and the retinal pigment epithelium. Our results suggest a role of these peptides both in the regulation of intraretinal fluid movement and--by analogy with other peptides--as possible neutrotransmittors. The localisation of ANP and BNP in the retinal pigment epithelium suggests that these peptides may influence ocular fluid homeostasis at the outer blood-retinal barrier by modulating pigment epithelial function.