Atrial natriuretic peptide binds to ANP-R 1 receptors in neuroblastoma cells or is degraded extracellularly at the Ser-Phe bond

Abstract

ANP-R 1 receptors for atrial natriuretic peptide (ANP) showed the following rank order of affinity in intact human neuroblastoma cells NB-OK-1: human ANP-(99–126)≈ human ANP-(102–126) ≈ rat ANP-(99–126) (K 1 17–32 pM) > human ANP-(103–126) > porcine brain natriuretic peptide (BNP). Analogues truncated at the C-terminal extremity or devoid of a disulphide bridge, such as rat ANP-(103–123), rat C-ANP-(102–121), rat ANP-(111–126), rat ANP-(99–109) and rat [desCys 105,Cys 121]ANP-(104–126) and chicken C-type natriuretic peptide, were not recognized. The occupancy of these high affinity ANP-R 1 receptors led to marked cyclic GMP accumulation in the presence of 3-isobutyl 1- methylxanthine. An ectoenzymic activity, partiy shed in the incubation medium, provoked the stepwise release of Phe-Arg-[ 125I]Tyr, Arg-[ 125I]Tyr and [ 125I]Tyr from rat [ 125I]ANPW-(99–126), at an optimal pH of 7.0. Its inhibition by 1,10-phenanthroline, EDTA and bacitracin but not by thiorphan suggests the contribution of at least one neutral metalloendopeptidase, distinct from EC 3.4.24.11, for which ANP showed high affinity.