Isolation and identification of vasopressin- and oxytocin-immunoreactive substances from bovine pineal gland. Presence of N alpha-acetyloxytocin.

Peptides with vasopressin- and oxytocin-immunoreactivity were purified from bovine pineal glands. Three immunoreactive peptides were purified by successive high performance liquid chromatography steps in sufficient quantities for identification by fast atom bombardment-mass spectrometry. Two peptides were characterized as authentic vasopressin and oxytocin. Their identities were in agreement with the observed immunoreactivities, high performance liquid chromatography behavior, and biological activity. The third peptide was identified as N alpha-acetyloxytocin. The presence of the acetyl group was demonstrated by the molecular mass of the peptide, and the N alpha position was shown to be the modified site by the presence of a blocked NH2 terminus. N alpha-Acetylation of oxytocin may be involved in altering the biological properties of the peptide.