An in vitro Action of Human Growth Hormone in the Presence of Actinomycin D

Abstract

THE in vitro addition of growth hormone to isolated diaphragm from the hypophysectomized rat stimulates the uptake of glucose^1–3, the incorporation into protein of natural amino-acids^3–5 and the accumulation in the tissue in an unchanged state of certain natural and unnatural amino-acids^6,7. These effects are similar to those of insulin on isolated diaphragm from the normal or the hypophysectomized rat⁸. Eboue-Bonis et al.⁹ have recently found that the action of insulin in vitro in promoting glucose uptake and the incorporation into protein of label from labelled natural amino-acids is still seen in the presence of actinomycin D—a powerful inhibitor of the synthesis of nucleic acid¹⁰. We have investigated the influence of actinomycin D on the effectiveness of human growth hormone in promoting the incorporation into protein of ¹⁴C from glycine-¹⁴C–U and into nucleic acid of ¹⁴C from orotic acid 6-¹⁴C, when the hormone is added in vitro to isolated diaphragm from hypophysectomized rats.