1. Binding sites for atrial natriuretic peptide (ANP) with a specificity similar to that of vascular ANP receptors have been demonstrated previously in human platelets. The density of these binding sites for ANP on platelets is decreased after increased dietary sodium intake, when plasma ANP levels increase. ANP-binding sites were investigated in patients with severe congestive heart failure (CHF), a condition in which there is an increase in the concentration of ANP in plasma.
2. In 24 patients with a clinical diagnosis of functional class III–IV CHF, plasma ANP (90.3 ± 13.4 fmol/ml, mean ± sem) was significantly higher (P < 0.001) than in 16 age-matched patients without cardiac disease (15.4 ± 2.0 fmol/ml). The density of ANP-binding sites on platelets was significantly lower (P < 0.01) in the 24 CHF patients (6.3 ± 0.8 fmol/109 cells) than in the non-cardiac patients (11.8 ± 1.4 fmol/109 cells). There was no significant difference in affinity of the ANP-binding sites between both groups. There was a significiant non-linear inverse correlation of the density of ANP-binding sites on platelets with plasma ANP concentration. These results could not be explained by prior receptor occupancy secondary to the elevated concentration of circulating ANP.
3. In conclusion, ANP-binding sites on platelets are decreased in patients with severe CHF and with significantly elevated concentration of ANP in plasma.