THE NEUROHYPOPHYSIAL HORMONES OF A REPTILE SPECIES, THE COBRA (NAJA NAJA)

Abstract

SUMMARY Purification of cobra neurohypophysial extracts has led to the isolation of two fractions with uterotonic activity. One of these was eluted from carboxymethylcellulose columns at the same place as oxytocin. Its amino acid composition and pharmacological properties are compatible with it being a mixture of oxytocin and 8-isoleucine oxytocin (mesotocin). The second fraction had the chromatographic properties of 8-arginine oxytocin (arginine vasotocin) and had the amino acid composition of this compound, but the degree of potentiation of its oxytocic activity by magnesium ions may imply the presence of yet another active peptide in this fraction.