Nα-Acetyl-Vasopressin- and Nα-Acetyl-Oxytocin-Like Substances: Isolation and Characterization in the Rat Neurointermediate Pituitary and Presence in the Brain

Post-translational modifications of vasopressin and oxytocin in pituitary and brain were investigated in view of recent evidence that oxytocin is partly N^α-acetyfated in the bovine pineal gland. Two peptides were isolated from the neurointermediate lobe of the rat pituitary gland and characterized as N^α-acetyl-vasopressin and N^α-acetyl-oxytocin, based on chromatographic and immunological properties as well as the blocked N-terminus. In the neurointermediate pituitary the acetylated forms represented approximately 1% of the vasopressin and oxytocin contents. These two peptides were also detected in some, but not all, investigated brain areas. The highest degree of acetylation was found in the pineal gland. In all regions acetylation of oxytocin was more abundant than that of vasopressin. The data indicate that acetylation of vasopressin and oxytocin generally occurs as a post-translational modification. They support the concept that acetylation may represent a mechanism aimed to control bioactivity of the neurohypophyseal hormones.