Preparation of Growth Hormone from a Rat Mammosomatotropic Pituitary Tumor¹

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 diethylaminoethyl cellulose chromatography and then by preparative polyacrylamide gel electrophoresis. The yield of material in the purest fraction was 44 µg/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 hormone fraction gave a 53-micron stimulation at a 0.15-mg dose level. Analytical polyacrylamide gel electrophoresis 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 purification obtained was 12-fold.