In Vivo Effects of Estrogen on Ovine Pituitaries: Prolactim and Growth Hormone Biosynthesis and Messenger Ribonucleic Acid Translation*

Abstract

PRL and GH biosynthesis was monitored in sheep in response to steroid treatment. Ovariectomized ewes were treated for 10 days with one of the following: oil vehicle, progesterone, estradiol cyclopropionate, or progesterone and estradiol in combination. The incorporation of radioactive leucine into PRL and GH was measured by electrophoresis on sodium dodecyl sulfate-polyacrylamide gels and immunoprecipitation. PRL production increased from 26% of total protein synthesis to 39% in estrogen-treated animals (an increase to 150% of control values), while GH synthesis was maintained at 5% of the total protein. Progesterone alone had no significant effect on either peptide and did not interfere with the estrogen-induced increase in PRL synthesis. To examine effects at the messenger RNA (mRNA) level, RNA was isolated from pituitaries and translated in the wheat germ system with radioactive leucine. Both immunoprecipitated PRL and GH cell-free products were larger than their respective standards on sodium dodecyl ...