PPARs are a family of nuclear hormone receptors involved in various processes that could influence ovarian function. We investigated the cellular localization and expression of PPARs during follicular development in ovarian tissue 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 removed 0, 4, 8, 12, and 24 h post-hCG to study the periovulatory period. mRNAs corresponding to the PPAR isotypes (␣, ␦, and ␥)

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... ere localized by in situ hybridization. Changes in the levels of mRNA for the PPARs were determined by ribonuclease protection assays. PPAR␥ mRNA was localized primarily to granulosa cells, and levels of expression did not change during follicular development. Four hours post-hCG, levels of mRNA for PPAR␥ decreased (P < 0.05) but not uniformly in all follicles. At 24 h post-hCG, levels of PPAR␥ mRNA were reduced 64%, but some follicles maintained high expression. In contrast, mRNAs for PPAR␣ and ␦ were located primarily in theca and stroma, and their levels did not change during the intervals studied. To investigate the physiologic significance of PPAR␥ in the ovary, granulosa cells from PMSG-primed rats were cultured for 48 h with prostaglandin J 2 (PGJ 2 ) and ciglitazone, PPAR␥ activators. Both compounds increased progesterone and E2 secretion (P < 0.05). These data suggest that PPAR␥ is involved in follicular development, has a negative influence on the luteinization of granulosa cells, and/or regulates the periovulatory shift in steroid production. The more general and steady expression of PPARs ␣ and ␦ indicate that they may play a role in basal ovarian function. (Endocrinology 142: 4831-4838, 2001)