Effect of vitrification and beta-mercaptoethanol on reactive oxygen species activity and in vitro development of oocytes vitrified before or after in vitro fertilization.

OBJECTIVE To investigate the effect of vitrification and beta-mercaptoethanol (beta-ME) on reactive oxygen species (ROS) activity and in vitro development of oocytes vitrified before or after in vitro fertilization (IVF). DESIGN Randomized prospective study. SETTING University-based assisted reproductive technology laboratory. ANIMALS(S): Abattoir-derived porcine ovaries. INTERVENTIONS(S) Oocytes were vitrified either before or 4 hours after the end of IVF by solid surface vitrification (SSV) without centrifugation and/or delipation procedure. beta-ME was used to inhibit ROS activity. MAIN OUTCOME MEASURES(S) Viability was evaluated by membrane integrity and esterase enzyme activity using fluorescein diacetate staining while ROS activity was assessed by 2',7'-dichlorofluorescein assay. RESULT(S) Vitrification increased the ROS activity and decreased the viability and in vitro development of vitrified oocytes. Addition of beta-ME to vitrification and culture medium partially annihilated the ROS activity but did not improve the viability of vitrified-warmed oocytes. Furthermore, beta-ME had no effect on improving the fertilization ability of oocytes vitrified at metaphase II stage but significantly increased their ability to cleave. beta-ME also increased the rate of cleavage and blastocyst formation ability of oocytes vitrified 4 hours after the end IVF. CONCLUSION(S) Vitrification increases ROS activity in oocytes that can be partially annihilated by beta-ME to obtain enhanced embryonic development.