Further characterization of growth hormone from the chum salmon (Oncorhynchus keta)

This report describes the isolation of growth hormone (GH) from the chum salmon (Oncorhynchus keta) pituitary using gel, affinity, and ion exchange chromatography. Chum GH has an estimated molecular weight of 23,500 and an amino acid composition that is consistent with a vertebrate GH. The differentially charged forms of chum GH which are only apparent under alkaline conditions were separated by ion exchange and compared immunologically and biologically; Peak I, which consists of a single band (Rf = 0.35) under alkaline electrophoresis and Peak II which consists of two bands with Rf's of 0.41 and 0.45. Both forms were found to be immunologically identical by immunodiffusion and to have similar growth promoting properties in intact rainbow trout (Salmo gairdneri). Chum GH was also active in the rat tibia test at a daily dosage of 70 micrograms/animal. The results are discussed in relation to previous studies with chum GH and other fish GHs.