Estradiol regulates the transcription of the prolactin gene

The effect of estradiol on prolactin gene transcription in pituitaries from ovariectomized, female rats has been investigated. Analysis of the multiple prolactin mRNA species present in pituitary cells demonstrated that estradiol increases the concentration of all the large, potential nuclear precursors of prolactin mRNA. To further examine possible estradiol effects on prolactin mRNA synthesis, nuclei were isolated from rat pituitaries and allowed to continue RNA synthesis in vitro in the presence of [alpha-32P]UTP. Newly synthesized prolactin mRNA sequences were quantitated by hybridization of [32P]RNA to immobilized plasmid DNA containing prolactin cDNA sequences. After 24 h of estradiol treatment, prolactin mRNA synthesis was increased 4-fold. Estradiol effects on prolactin gene transcription were detected as early as 20 min after injection of the steroid. These findings suggest that estradiol increases prolactin mRNA levels by increasing the transcription of the prolactin gene.