Dose and Time Dependent Effect of N-Acetyl-L-Cysteine Supplementation on In Vitro Fertilization of Bovine Oocytes

In vitro fertilization (IVF) is a process that is exposed to high oxygen concentration (20%) resulting in the production of reactive oxygen species (ROS). N-acetyl-L-cysteine (NAC) is a potent free radical scavenger. However, it is reported that NAC supplementation during IVF has no or detrimental effect on oocyte development. The present study was designed to evaluate the effects of different concentrations of NAC supplemented at different stages of in vitro culture of bovine oocytes on fertilization rate and polyspermy. In Experiment 1, NAC was added at a fixed concentration (1.25 mM) to IVM medium (Group NAC IVM+/IVF-), to the fertilization medium (Group NAC IVM-/IVF+) and in both mediums (Group NAC IVM+/IVF+). In experiment 2, NAC was added only to the IVF medium at higher concentrations (5mM and 10mM). The control group were processed without the addition of NAC in mediums.In the present work, NAC (1.25mM) negatively influenced the rate of fertilized oocytes only in a NAC IVM+/IVF+ Group, while in Groups NAC IVM+/IVF- and IVM-/IVF+ a significant greater rate of normal fertilized oocytes has been recorded.In conclusion from the results of the present study we can state that addition of low doses of NAC (1.25 mM) to the IVM or IVF medium has positive effects on the quality of the fertilized oocytes by reducing polyspermic rates, while doses greater than 5 mM in IVF medium demonstrated a detrimental effect on the fertilization rate.