Independent Regulatory Influence of Growth Hormone on the Hepatic Synthesis of α2u-Globulin*

Abstract

Administration of GH through sc injections to hypophysectomized male rats induces the hepatic mRNA for alpha 2u-globulin (a male-specific urinary protein) from an undetectable level to 43.4% of the normal male level. The same treatment administered to hypophysectomized-gonadectomized rats and androgen-insensitive Tfm rats induces alpha 2u-globulin mRNA to a level of only 5-10% of that in the normal male. However, none of these types of animals shows an appreciable response when GH is administered continuously through osmotic minipumps. Perfusion of the livers derived from hypophysectomized male rats with the blood from hypothyroid rabbits (also deficient in GH) was used to examine in vitro effects of GH on alpha 2u-globulin synthesis. Supplementation of the perfusion medium with GH and T4 failed to induce alpha 2u-globulin within the perfusion period of 120 min. These results show that GH can influence alpha 2u-globulin synthesis independent of the androgen and that the mode of administration of GH plays an important role in its biological response.