Rapid androgenic stimulation of α_2u-globulin synthesis in the perfused rat liver

Hepatic synthesis of α0_2u-globulin and its mRNA in the male rat is dependent on androgen, glucocorticoid, T₄, insulin, and GH. Some of these hormones may act directly on the liver, while others may influence aâ§-globulin synthesis through indirect physiological changes. In the present study the specific role of androgen in the synthesis of α_2u-globulin was examined in an in vitro liver perfusion system. The addition of 5a-dihydrotestosterone to the medium perfused through livers from castrated rats resulted in a rapid increase (-10-fold over the vehicle control within 120 min) in the circulating level of a⧠globulin. Labeling with [³⁵S]-methionine showed that the androgen- mediated increase in the circulating level of α_2u-globulin is due to release of the newly synthesized protein. Quantification of α_2u-globulin mRNA in the perfused livers with and without androgen supplementation indicated that the increased mRNA level can only partially account for the elevation of the circulating level of this protein. From these results it is concluded that androgen can act directly on the liver to stimulate α_2u-globulin synthesis, and the hormone may influence more than one regulatory step.