Expression and localization of PPARs in the rat ovary during follicular development and the periovulatory period

PPARs are a family of nuclear hormone receptors involved in various process es that could influence ovarian function. We investigated the cellular loca lization and expression of PPARs during follicular development in ovarian t issue collected from rats 0, 6, 12, 24, and 48 h post-PMSG. A second group of animals received human CG (hCG) 48 h post-PMSG. Their ovaries were remov ed 0, 4, 8, 12, and 24 h post-hCG to study the periovulatory period. mRNAs corresponding to the PPAR isotypes (alpha, delta, and gamma) were localized by in situ hybridization. Changes in the levels of mRNA for the PPARs were determined by ribonuclease protection assays. PPAR gamma mRNA was localized primarily to granulosa cells, and levels of e xpression did not change during follicular development. Four hours post-hCG , levels of mRNA for PPAR gamma decreased (P < 0.05) but not uniformly in a ll follicles. At 24 h post-hCG, levels of PPAR gamma mRNA were reduced 64%, but some follicles maintained high expression. In contrast, mRNAs for PPAR alpha and delta were located primarily in theca and stroma, and their leve ls did not change during the intervals studied. To investigate the physiolo gic significance of PPAR gamma in the ovary, granulosa cells from PMSG-prim ed rats were cultured for 48 h with prostaglandin J(2) (PGJ(2)) and eiglita zone, PPAR gamma activators. Both compounds increased progesterone and E2 s ecretion (P < 0.05). These data suggest that PPAR gamma is involved in follicular development, h as a negative influence on the luteinization of granulosa cells, and/or reg ulates the periovulatory shift in steroid production. The more general and steady expression of PPARs alpha and delta indicate that they may play a ro le in basal ovarian function.