12 - Natriuretic Peptide Receptors

Abstract

Natriuretic peptides play a central role in the regulation of body fluid and electrolyte balance. Binding experiments and cross-linking and autoradiographic studies have confirmed the existence of receptors on astrocytes. The dissociation between the binding affinity and cGMP responses remains unexplained. One possibility is the presence of astrocytic receptor subtypes to natriuretic peptides with the 66-kDa peptide as the predominant form that is uncoupled to guanylate cyclase. Apart from coupling to guanylate cyclase, atrial natriuretic peptide (ANP) receptors have been shown to have a clearance function and to affect phosphatidylinositol metabolism in other tissues. Natriuretic peptides inhibit astroglial proliferation. However, it remains to be clarified whether this inhibitory effect is mediated through the clearance receptors, which could act by enhancing phosphatidylinositol turnover, or the guanylate cyclase-coupled receptors, as in the case of other tissues. A C-type natriuretic peptide (CNP) is present at high concentrations in the brain but not peripheral tissues and may act mainly as a neurotransmitter/neuromodulator. It is 10–20 times more efficacious than ANP and brain natriuretic peptide (BNP) in its maximal stimulatory effect on cGMP release from mouse astrocytes in culture.