RELATIONSHIP OF THE DIABETOGENIC ACTIVITY OF OX PITUITARY EXTRACTS TO THEIR GROWTH HORMONE CONTENT

Abstract

Different batches of crude bovine pituitary extract were compared with respect to the 'D/G ratio', i.e. the ratio of diabetogenic activity in cats to growth-promoting activity in rats. The ratio was low for some extracts which had been incubated as in the experiments of Marks & Young [1940], but wide variations were found with 'normal' (non-incubated) extracts, for some of which the ratio was notably high. Purified preparations of the diabetogenic factor isolated from crude extracts appeared to consist predominantly of growth hormone (GH), as shown particularly by examination in the ultracentrifuge (see Addendum). The possibility that 'purified GH' might, in common with crude extracts, vary in D/G ratio, received little support from tests performed on semi-purified GH fractions isolated from crude extracts, or on purified GH preparations subjected to mildly destructive treatments such as incubation with carboxypeptidase, which did not impair either diabetogenic or growth-promoting activity. Tests with the GH preparation (pig) of Raben & Westermeyer [1952] did not confirm their claim that it lacks diabetogenic activity. The growth-promoting activity of GH is reduced by ACTH or posterior-pituitary extract, and enhanced by thyrotrophin. The diabetogenic activity of GH is known to be enhanced by ACTH under certain conditions. Variations among crude extracts in D/G ratio may thus be attributable to variations in the content of certain hormones other than GH. Data are presented for changes in body-weight in cats treated with crude pituitary extracts or purified GH.