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 ( R f = 0.35) under alkaline electrophoresis and Peak II which consists of two bands with R f'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 μg/animal. The results are discussed in relation to previous studies with chum GH and other fish GHs.