1. The possible mechanism of the oestrogenic inhibition of the androgen-dependent synthesis of alpha2u-globulin in rat liver was explored by a correlative study of the amounts of alpha2u-globulin, its corresponding mRNA and circulating testosterone in oestrogen-treated male rats. 2. Daily treatments of mature male rats with oestradiol-17beta (10 microgram/100g body wt.) decreased and ultimately stopped the hepatic synthesis of alpha2u-globulin as determined by both hepatic and urinary concentrations of the protein. The oestrogen-mediated decrease in the hepatic synthesis of alpha2u-globulin was correlated with a decrease in the mRNA for this protein. 3. Withdrawal of oestrogen resulted in the recovery of alpha2u-globulin synthesis and an increase in mRNA for alpha2u-globulin. 4. At higher doses of oestradiol-17beta (50 microgram/100g body wt.), synthesis of alpha2u-globulin was totally suppressed. In addition, this treatment resulted in an extended period of androgen-insensitivity during which treatment with androgens induced synthesis of neither alpha2u-globulin nor its corresponding mtrna. 5. it is concluded that the oestrogenic inhibition of alpha2u-globulin synthesis is mediated by an oestrogen-dependent decrease in the hepatic content of translatable mRNA for alpha2u-globulin.
