Structure-activity relationships of atrial natriuretic factor (ANF). I. Natriuretic activity and relaxation of intestinal smooth muscle.

Atrial natriuretic factor-related peptides were produced from synthetic ANF (101-126) either by chemical hydrolysis at the N-terminal end or by treatment with carboxypeptidases at the C-terminal end. The biological activities of these peptides were characterized in vivo by a natriuretic bioassay and in vitro by relaxation of contracted intestinal smooth muscle (chick rectum). In the natriuretic assay, the removal of Asn122, Ser123 and Phe124 at the C-terminal end alters considerably the renal response. Deletion or extension of amino acids at the N-terminal end affects only slightly the natriuretic activity. Removal of N-terminal or C-terminal amino acids decreases the relaxant activity of ANF on the chick rectum. In both bioassays, simultaneous deletions of residues at both ends drastically affect the activity in an additive manner.