INDUCTION AND ACTIVATION OF STAT-5 IN THE OVARIES OF PSEUDOPREGNANT RATS

PRL acts in the ovary to promote the maintenance and function of the c orpus luteum. However, the cellular signals that induce these response s have not been clearly defined. In the present report we demonstrate that Stat 5, previously identified as a transcription factor activated by PRL in the mammary gland, is also activated by PRL in the ovaries of pseudopregnant rats. Intraperitoneal injection of PRL into pseudopr egnant rats results in the tyrosine phosphorylation and nuclear transl ocation of Stat 5. This activated Stat 5 possesses DNA-binding activit y for a sequence containing the PRL-inducible element. In addition, we report that luteinization of the PMSG-primed ovary by the administrat ion of hCG is accompanied by an induction of Stat 5 protein.