Novel atrial natriuretic/vasodilator polypeptides

A polypeptide compound useful as a natriuretic, diuretic, and/or vasodilator in mammals, said polypeptide compound having the formula:

• ##STR33## wherein X is hydrogen, amido, acetyl, or an oligopeptide of up to 125 amino acid residues from the naturally occurring N-terminal Atrial Peptide Sequence, including the N-acetyl derivatives thereof;
• Y is hydroxyl, amido, Asn-OH, Asn-Ser-OH, Asn-Ser-Phe-OH, Asn-Ser-Phe-Arg-OH, Asn-Ser-Phe-Arg-Tyr-OH, or the C-terminal amide derivatives thereof;
• or an oligopeptide extension of up to 20 amino acid residues from the C-terminus of any of the foregoing, including the C-terminal amide derivatives thereof;
• each of AA.sub.6, AA.sub.7, AA.sub.13, and AA.sub.17 is independently selected from the group consisting of Gly and Ala;
• AA.sub.9 is selected from Ile, Met, and Val;
• and AA.sub.12 is selected from Ile and Val,
• wherein 0, 1 or 2 are by the D-isomer thereof, and including such compound containing a disulfide bridge joining the cysteine residues and the pharmacologically acceptable salts thereof,
• with the proviso that when AA.sub.6, AA.sub.7, AA.sub.13, and AA.sub.17 are Gly, AA.sub.9 is Ile or Met, AA.sub.12 is Ile, and Y is AsnOH, Asn-Ser-OH, Asn-Ser-Phe-OH, Asn-Ser-Phe-Arg-OH or Asn-Ser-Phe-Arg-Try-OH or the C-terminal amide derivatives thereof, and X is H or contains Arg as its C-terminal amino acid, at least one of the residues must be replaced by the D-isomer thereof.