We are continuing to study the mechanism of prolactin biosynthesis in the pituitary. In particular, we are concerned with changes in prolactin biosynthesis that occur after estrogen administration. These changes appear to be due to increases in mRNA for pre-prolactin. We now need to study the mechanisms involved in this increased mRNA concentration. Several possibilities must be considered including changes in mRNA turnover, precursor RNA processing and regulation at the level of gene transcription. The latter seems a most likely possibility but the others must be considered. Studies will be initiated to see if changes in prolactin gene transcription can be assessed. We also hope to start looking at early changes in nuclear function in estrogen stimulated pituitaries.