Female Reproductive Tract

Antioxidant Defenses Are Modulated in the Cow Oviduct During the Estrous Cycle

Abstract

The balanced presence of reactive oxygen species and antioxidants has a positive impact on sperm functions, oocyte maturation, fertilization, and embryo development in vitro. The mammalian oviduct is likely to provide an optimal environment for final gamete maturation, sperm-egg fusion, and early embryonic development. However, the expression and distribution of antioxidant enzymes in the bovine oviduct are poorly characterized. In this study, we analyzed the mRNA expression and enzymatic activities of major antioxidants (glutathione peroxidase [GPx], superoxide dismutase [Cu,ZnSOD], and catalase) in the bovine oviduct throughout the estrous cycle. We found high levels of expression for GPx-3 in the isthmus in contrast to GPx-1 and GPx-2, which were mostly expressed in the ampulla and infundibulum of the oviduct. The highest levels of mRNA expression for GPx-1 were observed toward the end of the estrous cycle before ovulation, while GPx-2 was mostly expressed at mid-cycle. Catalase and Cu,ZnSOD mRNA analyses revealed a homogenous expression along the oviduct. We also discovered the highest levels of glutathione and enzymatic activities for GPx and catalase at the middle (10-12 days) and the end (18-20 days) of the estrous cycle in contrast to total SOD activity, which remained constant throughout the estrous cycle in the oviductal fluids. This work underlines the importance of hydrogen peroxide and hydroperoxide removal by GPx in the oviduct. The heterogeneous expression of antioxidants such as GPx along the oviduct is a possible indication of their physiological role in the events leading to successful fertilization and implantation in vivo.