Isolation and partial characterization of growth hormone from fin whale pituitary glands

A highly purified somatotropin (growth hormone) has been isolated from fin whale (Balaenoptera physalus) pituitary glands in a yield of 1,014 mg/kg of wet weight tissue. The preparation was shown to be homogenous by isoelectric focusing on polyacrylamide with growth-promoting potency comparable to that of ovine growth hormone by the rat tibia test. The molecular weight was found to be 20,000 daltons by SDS gel electrophoresis and 40,000 daltons by exclusion chromatography on Sephadex G-100 at pH 8.2. The amino acid composition and alpha-helix content of fin whale somatotropin were similar to those of human, bovine, and ovine hormones. The circular dichroism in the side chain region, however, differed from those of the mammalian hormones. The NH2-terminal amino acid sequence was nearly identical with those of the bovine and ovine hormones as determined by the fluorescein isothiocyanate method.