Decreased Number and Affinity of Rat Atrial Natriuretic Peptide (6-33) Binding Sites in the Subfornical Organ of Spontaneously Hypertensive Rats

Abstract

Binding sites fo¡ rat atrial natriuretic peptide (6-33) were quantified by incubation of brain sections with (3-f'?5uiodot'.rosyl23) ¡at atrial natriuretic peptide (6-33), followed by autoradiography with computerized microdensitometry. Spontaneously hypertensive tats presmt lowe¡ numbe¡s and lower affinity of binding sites than normotensive controls, Wista¡-Kyoto rats, in the subfomical organ (binding capacity 61.7 t 8.9 and 124.3 + 10.7 fmol/mg protein; affinity constant 4.25 a 0.55 and 11.10 t 1.67 X 10e M-t, respectively). In the choroid plexus, hypertensive ¡als have lower numbers of sites than normotensive rats (binding capacity 72.7 ! 10.5 and 173.6 i 22.8 fmol/mg protein, respectively), but there was no difference in the binding affinity (affinity constant 6.28 a 0.82 a d 7.60 ! 2.06 x loe M-1, resp€ctively). Our results suggest that discretelt locaüzed brain binding sites for tat atrial natriuretic peptide (6-33) may have a physiological function in genetically hyper.tensive rats. (Circ Res 58: 389-392, 79861