THE TRANSCRIPTION FACTOR C EBP-BETA AND ITS ROLE IN OVARIAN-FUNCTION - EVIDENCE FOR DIRECT INVOLVEMENT IN THE OVULATORY PROCESS/

Gonadotropins are responsible for maturation of the ovarian follicle a nd the oocyte. Ovulation is the ultimate step in this process and invo lves disintegration of the follicular wall and subsequent release of a n oocyte into the oviduct. These events are triggered by a surge of lu teinizing hormone (LH), Genes expressed in the ovary, that respond to LH, are likely to be involved in the biochemical pathways that regulat e ovulation, The transcription factor C/EBP-beta is induced promptly i n the ovary, as a response to an ovulatory dose of gonadotropins. We u sed an ex vivo perfusion system to demonstrate that a specific reducti on in ovarian C/EBP-beta expression inhibits ovulation, In such ovarie s the oocytes appeared to be entrapped within the follicle. We have fo und a correlation between the expression level of the activating isofo rm of C/EBP-beta and the number of oocytes ovulated in response to gon adotropins, Since a reduction in C/EBP-beta expression does not affect the level of the ovulatory mediator prostaglandin endoperoxide syntha se-2 (PGS-2), these findings support the view of C/EBP-beta as an impo rtant factor in the ovulatory process and highlight a C/EBP-beta-depen dent and PGS-2-independent pathway that takes part in regulation of ov ulation.