Spatiotemporal expression and hormonal regulation of antioxidant enzymes in the bovine oviduct epithelium.

The oviduct provides an optimal environment to protect gametes and embryos against oxidative stress, yet its endogenous defenses remain insufficiently characterized. This study examined the expression and the spatial, temporal and hormonal regulation of four major antioxidant enzyme families - peroxiredoxins (PRDX), catalase (CAT), superoxide dismutases (SOD), and glutathione peroxidases (GPX) - in the bovine oviduct. Oviducts from cyclic cows were analyzed in three complementary experiments. In vivo (Experiment 1), mRNA expression of antioxidant enzymes (CAT, GPX1-3, PRDX1-6, SOD1-2) was compared between oviductal regions (ampulla vs. isthmus) and estrous cycle stages (pre-ovulatory, post-ovulatory, luteal). In vitro (Experiment 2), physiological concentrations of progesterone (100 ng/mL) and estradiol (300 pg/mL) were tested on gene expression in ampullary and isthmic epithelial spheroids. In Experiment 3, GPX protein abundance and enzymatic activity were assessed in oviductal fluid. All transcripts were detected in the oviduct epithelium. GPX1-3 and PRDX6 showed region-specific expression, with GPX1-2 enriched in the ampulla and GPX3 and PRDX6 in the isthmus. Stage-dependent variations were observed for CAT, SOD2, PRDX2, PRDX4, and PRDX6 in a region-dependent manner. Progesterone upregulated GPX2 and PRDX6 in both ampullary and isthmic spheroids, while estradiol selectively stimulated PRDX4 expression in isthmic spheroids. GPX3 protein abundance decreased at the post-ovulatory stage, in both regions, and mirrored the GPX activity in the oviduct fluid. These results demonstrate that antioxidant enzyme expression in the bovine oviduct is dynamically regulated by region, cycle stage, and hormonal milieu, highlighting their role in maintaining redox homeostasis during early reproductive events.