Preparation of Growth Hormone from a Rat Mammosomatotropic

Rat growth hormone was extracted from an acetone powder of transplantable mammosomatotropic pituitary tumors using buffered ammonium sulphate. Active material, precipitated by increasing the ammonium sulphate concentration to 1.5 M, was fractionated first by diethylaminoethyb cellulose chroma tography and then by preparative polyacrylamide gel electro phoresis. The yield of material in the purest fraction was 44 pg/gm wet weight of starting material. Tibia assays showed that the crude extract gave a 60-micron stimulation in cartilage width at a 2.0-mg dose level, whereas the purest growth hor mone fraction gave a 53-micron stimulation at a 0. 15-mg dose level. Analytical polyacrylamide gel ebectrophoresis at pH 9.5 indicated that the tumor growth hormone migrated more rapidly than growth hormone isolated from pituitaries; a single, but rather broad band was observed. The overall purifi cation obtained was 12-fold.