p53 tumor suppressor gene expression in the mouse ovary during an artificially induced ovulatory cycle.

Objective: To evaluate the expression of p53 in the mouse ovary during an artificially induced ovulatory cycle.

Study Design: Ovulation induction was performed using pregnant mares' serum gonadotropin/human chorionic gonadotropin (PMSG/hCG). First, a p53 promoter-chloramphenicol acetyl transferase (CAT) transgenic mouse model was used. Protein samples from ovaries of transgenic mice were assayed for CAT activity as evidence of p53 promoter activation. Next, RNA extracted from CD-1 mouse ovaries was used for reverse transcription/polymerase chain reaction (PCR) and northern blot analysis using a p53-specific probe.

Results: Increased CAT activity was noted in transgenic mice treated with PMSG/hCG as compared with controls. PCR studies on transgenic mice using primers for CAT and on CD-1 mice using primers for wild type p53 substantiated this observation. Furthermore, CAT assay and northern analysis, performed on samples obtained at serial time intervals from induction, indicated that maximal p53 expression occurs around the time of ovulation, beginning 48 hours after PMSG and peaking 6-12 hours after hCG administration.

Conclusion: The temporal expression of p53 in the ovary during a PMSG/hCG artificially induced ovulatory cycle may indicate a role for p53 in processes of differentiation of granulosa cells into luteal cells.