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 a rtificially induced ovulatory cycle. STUDY DESIGN: Ovulation induction was performed using pregnant mares' serum gonadotropin/human chorionic gonadotropin (PMSG/hCG). First, a p53 promote r-chloramphenicol acetyl transferase (CAT) transgenic mouse model was used. Protein samples from ovaries of transgenic mice were assayed for CAT activ ity as evidence of p53 promoter activation. Next, RNA extracted from CD-I m ouse 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 P MSG/hCG as compared with controls. PCR studies on transgenic mice using pri mers for CAT and on CD-I 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 h ours after PMSG and peaking 6-12 hours after hCG administration. CONCLUSION: The temporal expression of p53 in the ovary during a PMSG/hCG a rtificially induced ovulatory cycle may indicate a role for p53 in processe s of differentiation of granulosa cells into luteal cells.