[Role of protein biosynthetic processes in realizing the action of sex steroids on the level of specific estrogen-binding protein in the rat liver].

The authors have assessed the life-span of special estrogen-binding rat liver protein (SEBP) through inhibition of it by long-term administration of cyclohexymid (C1) and have examined how C1 affects the efficiency with which sex steroids influence the level of SEBP. The level of SEBP synthesis was assessed by the changes in the number of SEBP estradiol (E2)-binding sites. The long-term C1 administration in the dose of 100 micrograms suppressed SEBP synthesis by an average of 82.4% with the half-life of SEBP being about 18 hr. Testosterone propionate (TP) and 5 alpha-dihydrotestosterone, but not E2, were found able to mediate enhanced SEBP levels in the liver of ovariectomized female rats. A single 200 micrograms dose of C1 administered 30 min prior to hormone injection caused significant decreases in the efficiency of SEBP-mediated androgen activities in the liver of ovariectomized female rats, in TP-induced stimulation of the SEBP level in the liver of castrated male rats and in E2 inhibitory effect on the SEBP level in the liver of mature males. It is concluded that de novo protein synthesis is necessary for the early manifestation of all the above mentioned effects of sex hormones on the SEBP level. Based on the data regarding the duration of SEBP life and the rate with which it affects the activity of sex steroids it is supposed that in the early stages of hormonally induced manifestations there are changes in biosynthesis of regulating protein rather than in SEBP itself.