Effect of cyproterone acetate on androgen dependent synthesis of α(2u) globulin in rats

Cyproterone acetate (CA, 2.5 mg/100 g body wt) inhibited androgenic induction of α(2u) globulin in spayed rats. In mature male rats, which normally produce α(2u) globulin, ten daily injections of CA did not inhibit synthesis of this protein. Long term treatment of mature male rats (two injections every week for 12 weeks) showed only slight inhibition of α(2u) synthesis after 10 weeks of CA treatment. CA also failed to compete with 5α dihydrotestosterone for the cytosol androgen binding protein of male rat liver. The inhibitory effect of CA on the primary induction of α(2u) globulin in the spayed rat and its lack of effect on continued synthesis of this protein in maximally induced mature male rats are consistent with the hypothesis of a two step mechanism for androgenic regulation of α(2u) synthesis, an initial CA sensitive step followed later by a CA insensitive step.