Effects of estradiol on translation activity of Poly(A)-rich RNA from pituitary tumor whose growth is inhibited by estradiol.

Fischer rats bearing s.c. MtTF4 pituitary tumor were treated for 15 days with Silastic implants containing or not 17 beta-estradiol. Poly(A)-rich RNA was translated in a rabbit reticulocyte lysate system. The translation products were analysed by one and two-dimensional polyacrylamide gel electrophoresis. It is shown that estradiol affects the translation activities of a limited number of mRNAs. Some of the effects observed, such as the stimulation of PRL mRNA and the relative inhibition of GH mRNA are similar to those previously reported in normal pituitary. Other modifications are specific of the pituitary tumor: the stimulation of the mRNA activities coding for 26,000 and 33,000 dalton proteins. These results indicate that the inhibition of tumor growth by 17 beta-estradiol is accompanied by a specific modulation of mRNA translation activity and is not a non specific toxic effect.