Abstract
The present study was conducted to evaluate effects of oxygen concentration and free-radical scavengers on in vitro development of bovine oocytes matured and fertilized in vitro. Oocytes were matured in TCM-199+10% FCS supplemented with hormones and granulosa cells, and were fertilized in vitro with frozen-thawed, swim-up separated, and heparin-treated spermatozoa. After insemination, oocytes were cultured for 8 days in SOFM supplemented with 10% HS and with 5 different SOD (super-oxide dismutase) levels (0 to 750 μg/ml) [Experiment 1] and 5 different catalase levels (0 to 100 μg/ml) [Experiment 2]. In Experiment 1, high levels of SOD (500 and 750 μg/ml) significantly (P<0.01) reduced the rates of blastocyst development. In Experiment 2, there was no significant difference on the develop-ment to the blastocysts stage among the catalase levels. In Experiments 3 and 4, effects of the addition of SOD+ catalase under two gas atmospheres (5% CO2, 5% O2, 90% N2 vs 5% CO2 in Air) were examined. The addition of the free-radical scavengers in the medium under 5% CO2, 5% O2, 90% N2 resulted in sig-nificantly (P<0.05) higher rate of blastocyst development than embryos cultured under 5% CO2 in Air. The free-radical scavengers did not improve the blastocyst development under 5% CO2 in Air. It appeared that the cause of the stress of high oxygen tension (20% O2) was not only due to the free radicals but also other undetermined inhibiting factors.
