Type B and type C natriuretic peptide receptors modulate intraocular pressure in the rabbit eye

We investigated (1) the in vivo functional significance of the type B (ANP(B)) and type C (ANP(C)) natriuretic peptide receptors in the rabbit eye by evaluating the effect of intracameral administration of C-type natriuretic peptide (CNP) and C-ANP-(4-23) on intraocular pressure, and (2) the action of CNP on guanylate cyclase activity in the rabbit ciliary process membranes. Atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) were also studied for comparison. We demonstrated that the natriuretic peptides decrease intraocular pressure and stimulate guanylate cyclase activity, CNP being the most potent. The duration of the effect of C-ANP-(4-23) on intraocular pressure reduction was almost 9-fold that of the BNP and 20-fold that of ANP and CNP effect. This ligand increased threefold the immunoreactive natriuretic peptides levels in aqueous humour. Our data demonstrate the presence of functional ANP(A) and ANP(B) receptors in the rabbit eye and that the ANP(C) receptor modulates the concentration of the natriuretic peptides in the aqueous humour.