Atrial natriuretic peptide vascular receptor: regulation of low-affinity binding by calcium

1. In the presence of calcium, both high- [dissociation equilibrium constant (K_d) 5.8 × 10⁻¹¹ mol/l] and low-(K_d 1.2 × 10⁻⁸ mol/l) affinity binding of atrial natriuretic peptide was detected on plasma membranes prepared from sodium-depleted rats.

2. In contrast, under calcium-free conditions only high-affinity binding (K_d 6.9 × 10⁻¹¹ mol/l) was detected.

3. The requirement for calcium for low-affinity binding suggests a different mechanism of action than that for the high-affinity receptor.