PURIFICATION OF A GROWTH HORMONE-INHIBITING FACTOR (GIF) FROM SHEEP HYPOTHALAMUS

Crude hypothalamic extracts were fractionated on Sephadex G-25. Fractions that inhibited the release of pituitary GH in vitro as determined by the tibia assay were lyophilized and chromatographed on a carboxy methyl cellulose column. A portion of the GH-inhibiting activity was not retained on the column. The remainder was well retained and was eluted by application of ammonium acetate buffer of increasing pH and ionic strength. This GH-inhibiting zone from the CMC column was relyophilized and filtered through an analytical column of Sephadex G-25. Highly purified GIF was recovered in the effluent from the column. The results indicate that GIF can be obtained in highly purified form by application of procedures that have been successfully used in the purification of other hypothalamic releasing factors. © 1969 S. Karger AG, Basel.