Development of rabbit zygotes cultured in protein-free medium with catalase, taurine, or superoxide dismutase.

The present study was designed to examine the influence of several potential antioxidants in a synthetic medium completely devoid of macromolecules. Antioxidants may be beneficial as additives to a synthetic medium because they could serve as scavengers of toxic free radicals in media lacking serum, serum albumin, or other macromolecules that may serve as scavengers in more complex media. Rabbit zygotes were cultured for 72 h at 39 degrees C in media containing varying concentrations of the anti-oxidants in a gas phase consisting of 5% CO2:95% humidified air. At 72 h embryo development was recorded, and embryos were fixed and stained with Hoechst 33342 DNA stain to facilitate counting of cells. In experiment 1, concentrations of catalase ranging from 250 to 1000 IU did not affect the proportion of zygotes developing into blastocysts or the cell number (p > 0.05). In experiment 2, 2.5-10 mM taurine increased the proportion of zygotes developing into expanding blastocysts (70-78% vs. 40% for controls) and increased cell number from 100 to 154-159 (p < 0.05). In experiments 3 and 4, superoxide dismutase was tested over a range of 100-2400 IU/ml. The response reached a plateau at 600 IU/ml, with positive responses in rate of embryo development and growth similar to that found with taurine in experiment 2. These studies indicate that culture of zygotes into blastocysts in a macromolecule-free medium with 5% CO2:95% air is substantially improved when agents that could serve as antioxidants are included. Other mechanisms of action are not excluded by these studies.