RAPAMYCIN, FK506 AND CYCLOSPORINE-A INHIBIT HUMAN PROLACTIN GENE-EXPRESSION

In this work we demonstrate that transcription of the human prolactin gene is inhibited by the immunosuppressants FK506 (IC50 = 25 nM), cycl osporin A (IC50 = 190 nM) and rapamycin (IC50 = 25 nM). Whereas the ef fect of FK506 and cyclosporin A is specific for prolactin gene transcr iption, rapamycin has a more general effect on transcription and/or tr anslation in pituitary cells. In view of recent work demonstrating the immunoactivating role of prolactin, these results suggest that inhibi tion of prolactin gene expression in the pituitary may contribute to t he mechanism of action of immunosuppressants.