Phenypressin (Phe2-Arg8-vasopressin), a new neurohypophysial peptide found in marsupials

Recent investigations on marsupial neurohypophysial hormones have revealed that species belonging to the Australian family Macropodidae and the American family Didelphidae have, apart from an oxytocin-like hormone, two vasopressin-like peptides which can be separated either by ion-exchange chromatography or chromatoelectrophoresis. The major pressor hormone of two Australian species, the red kangaroo (Macropus rufus) and the tammar (Macropus eugenii), has been identified as lysine vasopressin by its amino acid sequence anda its pharmacological properties. We report here that the minor pressor hormone, which chromatographs on Amberlite CG-50 like arginine vasopressin, differs from it in sequence only at position 2 where phenylalanine replaces the tyrosine of arginine vasopressin.