DIVERGENT REGULATION OF GONADOTROPIN SUBUNIT MESSENGER-RNA LEVELS BY ANDROGENS IN THE FEMALE RAT

To examine the effects of gonadal steroids on the pretranslational regulation of the gonadotropin subunits in the female, adult female rats, beginning 7 or 28 days after ovariectomy, received daily injections of testosterone propionate (T), dihydrotestosterone propionate (D), or estradiol benzoate (E) for 7 days. Intact cycling females and ovariectomized rats that received vehicle served as controls. Serum was obtained for LH and FSH levels to assess changes in gonadotropin secretion. Total RNA from individual rats was recovered and analyzed by blot hybridization with specific radiolabeled cDNA probes for the α, LHβ, and FSHβ subunits. Autoradiographic bands were quantitated and standardized to mRNA levels in the intact animals. Ovariectomy resulted in a rise in serum gonadotropin levels and all three gonadotropin subunit mRNA levels. Estrogen replacement resulted in suppression of α, LHβ, and FSHβ mRNAs whether given at 7 or 28 days after ovariectomy. In contrast, whereas androgen replacement decreased α and LHβ mRNAs, D or T did not consistently suppresss FSHβ mRNAs. We conclude that chronic estrogen admnistration to the castrated female rat uniformly suppresses all three gonadotropin subunit mRNA levels. In female rats, as in male rats, chronic androgen administration fails to negatively regulate FSHβ mRNAs.