Studies on the corticotrophin releasing activity of a posterior pituitary extract

The posterior pituitary gland is considered to be a source of a corticotrophin releasing factor(s) distinct from vasopressin. In this study, the corticotrophin releasing activity of a commercial posterior pituitary extract (Pitressin) and synthetic vasopressin were compared, using a perfused rat pituitary monolayer system. Pitressin was shown to have approximately twice the releasing activity than could be accounted for by its vasopressin content. Fractionation of the posterior pituitary extract, using high pressure liquid chromatography, showed it to contain active material co-eluting with synthetic vasopressin, and at least three other corticotrophin releasing factors. The releasing activity of the most active of these factors was investigated and was found to stimulate ACTH release in a dose-related manner.