Development of more potent atrial natriuretic factor (ANF) analogs

Four modified atrial natriuretic factor (ANF) analogs were designed and synthesized by the solid-phase method. Using human ANF-(99-126) as the reference compound the receptor binding affinity and biological activity of these analogs were examined by radioreceptor assay and in vivo experiments. PLO68, a 21 amino peptide with structural modifications des-Ser103,104-[Mpr105,D-Ala107,114]APII-amide exhibited 2.5 and 2.2 fold more activity than human ANF-(99-126) in lowering blood pressure and causing natriuresis in urethane anesthetized rats. Receptor binding assays using rat lung membranes showed that PLO68 had a Kd of 200 +/- 12 pM compared to a Kd of 620 +/- 12 pM for human ANF-(99-126). Similar chemical modifications, except for substitution of glycine and alanine at the positions 115 and 118, and 120 by D-alanine resulted in three analogs PLO63 and PLO64, PLO67 respectively. PLO63, PLO64 and PLO69 had similar affinities and in vivo potency as human ANF-(99-126). These data suggest that the structural modifications made in PLO68 can cause an increase in the receptor binding ability and an enhancement of biological activities.