THE EFFECT OF DIFFERENT CONCENTRATIONS OF ETHYLENE GLYCOL ON ULTRA-RAPID FREEZING OF PIG OOCYTES

Abstract

The objective of this study was to investigate the effect of different concentrations of ethylene glycol on the normality and the in vitro maturation of pig oocytes, after ultra-rapid freezing on a microscope copper grid. Immature pig oocytes were exposed to different concentrations of ethylene glycol at levels of 4.0, 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0 molar for 20 seconds, at room temperature (25 oC), laid on a microscope copper grid and then plunged directly to -196 oC where they were kept for 10 seconds. The oocytes normality after thawing and the percentage that show in vitro maturation (MII)
were assessed by culturing them in TCM 199+NaHCO3 for 40-44 hrs at 38.5oC in a CO2 incubator. The results showed that ninety percent normality was found in the pig oocytes exposed to 4.0, 4.5, 5.0, 5.5 and 6.0 molar and the same results were seen in the in vitro maturation rates, which were 21.7, 24.5, 24.4, 20.9 and 19.3% respectively. These results were significantly better than those which used 6.5 and 7.0 molar ethylene glycol which were 85.6% and 78.7% (p <0.01) for the normality rates and 16.0% and 11.4% (p <0.05) for the maturation rates. The study indicated that the concentration of
ethylene glycol influenced the normality and the ability of immature pig oocytes to develop in vitro. The higher concentrations from 6.5 molar and up affected the oocytes after freezing.