Purification of Hypothalamic Melanocyte-Stimulating Hormone (MSH)-Releasing Factor with Sephadex. ∗

Summary

Acetone powders prepared from ovine stalk-median eminence tissue were extracted with glacial acetic acid and the glacial acetic acid extract was lyophilized. An ammonium acetate extract of the resultant pow-der was filtered through a column of Sepha-dex G-25. The eluent was assayed for its ability to deplete the pituitary of MSH. Extracts were injected i.v. into normal male rats which were sacrificed 20 minutes later. The MSH activity in pituitaries from rats receiving extracts was compared to that found in pituitaries from diluent-injected controls. MSH activity was estimated in an in vitro assay by microscopic grading of the melano-cytes. An active zone was eluted from the column. At the peak of this zone 65-70% of the MSH activity had disappeared from the pituitaries of the test rats. The MSH-releasing zone was separated from the zones which contained CRF, GH-RF, LH-RF, PIF and vasopressin, but overlapped the zone which contained FSH-RF. It was concluded that MSH-RF can be added to the family of hypo-thalamic polypeptides which influence adeno-hypophyseal secretion.