Follicular fluid hydrogen peroxide and lipid hydroperoxide in bovine antral follicles of various size, atresia, and dominance status

Abstract

To avoid inducing a state of oxidative stress (OS), assisted reproductive technologies (ART) must maintain a balance of reactive oxygen species (ROS) and antioxidants during the in vitro culture of oocytes. However, oocyte requirements and tolerance thresholds for ROS during in vivo development are still unclear. Previous studies have examined ROS levels in follicular fluid (FF) using pooled samples or according to follicle size. This study sought to examine two OS markers, lipid hydroperoxides (LPO) and hydrogen peroxide (H2O2), in FF of individually sampled follicles from bovine ovary pairs according to follicle size, atresia, and dominance status. TUNEL and cleaved Caspase-3 labeling were used to identify apoptotic granulosa cells and determine follicle atresia status. LPO were measured directly for the first time in FF. Non-atretic follicles and dominant follicles contained more FF H2O2 than atretic follicles and corresponding subordinate follicles, respectively. FF LPO did not vary in relation to atretic status, and no difference existed between dominant and subordinate follicles. However, FF LPO was significantly lower in first subordinate follicles than in the second subordinate follicles from each ovary pair. Neither H2O2 nor LPO levels correlated with follicle size. These data provide clear evidence that the events of antral folliculogenesis are relevant to ROS dynamics in vivo. Furthermore, such studies will help to optimize in vitro conditions for oocyte culture protocols, particularly when combined with a comparison of oocyte quality with respect to source follicle characteristics.