Expression of glycine cleavage system and effect of glycine on in vitro maturation, fertilization and early embryonic development in pigs

Glycine is the amino acid with the highest concentration in sow oviduct fluid, uterine fluid and follicular fluid. In this study, the effect of glycine on in vitro maturation, fertilization and early embryonic development in pigs was evaluated. In addition, the expression of T-protein, a component of the glycine cleavage enzyme system, was studied in the oocytes, cumulus cells, granulosa cells and oviductal epithelial cells using the methods of reverse transcription-polymerase chain reaction (RT-PCR). The results showed that supplementation of porcine oocytes with glycine during in vitro maturation improved on the development of embryos in vitro. After fertilization, glycine also enhanced embryo cleavage rate in the presence, but not in the absence, of oviductal cells. PCR product corresponding to T-protein was found in uncultured oocytes, cumulus cells, granulosa cells and oviductal epithelial cells. These results indicate that glycine is an important amino acid for the in vitro oocyte maturation, fertilization and early embryonic development in pigs.