PROFILING OF THE SUPEROXIDE DISMUTASE ANTIOXIDANTS IN BOVINE FOLLICULAR FLUIDS FROM DEVELOPING ANTRAL FOLLICLES

Abstract

In vivo, follicular fluid bathes the granulosa cells and cumulus-oocytecomplex. Not surprisingly, components of follicular fluid can promote oocyte development; however, the exact mechanism by which the fluid is beneficial remains unknown. The content of follicular fluid varies dynamically during antral folliculogenesis, and its use in modeling culture medium formulation has been recognized, albeit not fully explored. Oxidative stress arises whenever there is an imbalance in proand anti-oxidants. In this respect, it is conceivable that follicular fluid assists in controlling levels of pro-oxidants within the follicle. Therefore, whether follicular fluid directly provides protection of follicle cells from oxidative damage remains to be ascertained. This study focuses on the profiling of follicular fluid for the central antioxidant superoxide dismutase (SOD) and its three isoforms (CuZn-SOD, Mn-SOD, and extracellular or EC-SOD). Given documented and predicted changes in metabolic requirements and oxygen tension during folliculogenesis, we hypothesized that a dynamic balance of antioxidants (specifically SODs) characterizes the follicular fluid of developing antral follicles. To test our hypothesis, follicular fluids were collected from antral follicles that were sized following dissection from bovine ovaries. Ovaries were obtained at random stages of follicular development and the estrous cycle. Each follicular fluid sample was subsequently analyzed for: (1) the total levels of SOD enzymatic activity, and (2) the expression and quantification of Cu, Zn-SOD, Mn-SOD, and EC-SOD by immunoblotting. Amounts of SOD protein and activity were then evaluated in accordance with: (1) the size of the antral follicle that the follicular fluid originated from (specifically at times when the developmental competency of oocytes is known to vary); and (2) recorded ovarian parameters (stages of follicular development and the estrous cycle). Our work contributes to the identification of novel factors that relates to oxidative stress and that may influence the normal function of granulosa cells and cumulus-oocyte-complexes. In future studies, efforts aimed at optimizing culture conditions will benefit from such knowledge of the natural environment within which oocytes develop. (poster)