Binding of atrial and brain natriuretic peptides in brains of hypertensive rats

Abstract

Displacement of bound [ 125I]α-atrial natriuretic peptide (α-ANP) by brain natriuretic peptide (BNP) was used to map receptors common to both peptides in rat brain by in vitro autoradiography. Both spontaneously hypertensive rats (SHR) and the normotensive Wistar-Kyoto control strain (WKY) were studied. In both strains, [ 125I]α-ANP bound densely to subfornical organ, choroid plexus and arachnoid mater. Binding at these sites in either strain was displaced similarly by 1 μM unlabelled α-ANP or BNP. However, no [ 125I]α-ANP was displaced by peptides unrelated to α-ANP or BNP. In WKY, both α-ANP and BNP competed with similarly high affinities for binding sites occupied by [ 125I]α-ANP. This was also true for SHR. However, SHR showed a substantial reduction in the maximum number of binding sites in the subfornical organ and choroid plexus which were competed for by the peptides. Therefore, BNP may be a significant high affinity ligand for brain receptors previously thought specific for atrial natriuretic peptides, including receptors which vary between WKY and SHR.