The participation of peroxisome proliferator-activated receptors (PPARs) in ovarian function in cattle is still not fully understood. The aim of this in vitro study was to determine: (i) the immunolocalization, mRNA expression and tissue concentration of PPARα, PPARδ and PPARγ in the bovine corpus luteum (CL) (n = 40) throughout the estrous cycle, and (ii) the involvement of PPAR in PGF2α-induced processes related to luteolysis. CL (n = 9) explants were cultured in the presence of PPAR antagonists (10-5 M) in combination with or without PGF2α receptor antagonist (10-5 M) and PGF2α (10-6 M). The mRNA and protein expression of PPARs was evaluated through qPCR, IHC, and ELISA, respectively. The results showed that PPAR mRNA and protein expression differed according to the luteal stages. PGF2α upregulated PPARδ and PPARγ mRNA expression in the bovine CL in vitro, whereas PPARγ increased the inhibitory effect of PGF2α by decreasing progesterone secretion and the mRNA expression of hydroxy-delta-5-steroid dehydrogenase, 3 β- and steroid delta-isomerase 1 (HSD3B1) in the CL explants; mRNA transcription of tumor necrosis factor α (TNFα) and inducible nitric oxide synthase (iNOS) was increased. The obtained results indicate that the mRNA and protein expression of PPARs changes in the bovine CL throughout the estrous cycle and under the influence of PGF2α. We suggest that isoform γ, among all examined PPARs, could be a factor involved in the regulation of PGF2α-induced processes related to luteolysis in the bovine CL. Further studies are needed to understand the role of PPAR in luteal regression in the CL of cattle.
Keywords: corpus luteum; cow; estrous cycle; luteolysis; peroxisome proliferator-activated receptor; prostaglandin F2α.