The effect of glutamine on the development of sheep embryos in vitro

The effects of glutamine (Gln) on the in vitro development of sheep embryos cocultured with sheep oviduct epithelial cells (SOEC) or cultured in medium alone were investigated. The in vitro development was evaluated after culture in synthetic oviduct fluid (SOF) medium to Day 6, and then the viability of some of the morula/blastocyst stage embryos was assessed by transfer into recipient ewes. In Experiment 1, sheep embryos were cultured from Day 2 to Day 6 in SOF containing 0 or 1 mM Gln with or without (SOEC) support in a 2 x 2 factorial design. An interaction was found between the effects of Gln and SOEC (P<0.001). The addition of Gln increased blastocyst formation (6%, 2 36 vs 35%, 11 31 ) and the rate of pregnancy (50%, 4 8 vs 100%, 5 5 ) when the embryos were cultured in medium alone, but had no beneficial effect in the presence of SOEC. In Experiments 2 and 3, sheep embryos were cultured from Day 1 to Day 6 in SOF supplemented with 1 mM Gln, with 1 mM alpha-ketoglutarate or without supplementation (control). In Experiment 2, no other amino acids were added, but in Experiment 3 SOF was supplemented with 19 other amino acids. In Experiment 2, when Gln was the only amino acid, the rate of blastocyst formation was increased by the addition of Gln (24%, 8 35 ), but alpha-ketoglutarate caused no increase in blastocyst formation (3%, 1 34 ) compared to the control group (6%, 2 34 ). In Experiment 3, when 19 other amino acids were added, neither Gln nor alpha-ketoglutarate affected the rate of blastocyst formation or the subsequent development of embryos in recipient ewes. These results showed that Gln, when used as a single amino acid, has a beneficial effect on the development of sheep embryos in serum free culture without somatic cells. The data suggest that Gln is used as a source of amino groups rather than as a source of energy since no beneficial effects were found when its deaminated carbon skeleton (alpha-ketoglutarate) was used or when other amino acids were present.