Characterisation of atrial natriuretic peptide receptors in bovine ventricular sarcolemma

Analysis of [¹²⁵I]-ANP binding data in an isolated bovine ventricular sarcolemmal membrane fraction revealed a single high affinity binding site (K_d approximately 5 × 10^-11 M). The ring deleted ANP analogue des [QSGLG]-ANP (4-23)-NH₂ bound with a 1000-fold lower affinity indicating the absence of C-type receptors in this preparation. ANP stimulated guanylate cyclase activity by up to 2-fold with half-maximal activation at approximately 10^-9 M. Crosslinking [¹²⁵I]-ANP to its receptor with disuccinimidyl suberate (DSS) revealed two radiolabelled bands of 120 kDa and 65 kDa on non-denaturing SDS-PAGE. Radioactive signals from both bands were lost by reducing the sample with β-mercaptoethanol prior to electrophoresis, in which case a radioactive fragment of < 5 kDa migrated with the dye front. These results suggest that the binding of ANP to both high and low molecular weight "receptor" proteins may be associated with the hydrolysis of the peptide.