GLYCINE AND METHIONINE TRANSPORT BY BOVINE EMBRYOS

As glycine is one of the most concentrated amino acids in the female g enital tract, we investigated its uptake by bovine in vitro matured/in vitro fertilised blastocysts in the presence of increasing concentrat ions of radiolabelled glycine. We also determined methionine uptake by in vitro and in vivo produced embryos. In our study, the hypothesis o f more than one site of enzyme activity for glycine substrate was not validated. We determined a V-max of 23.4 fmol/min per embryo and a K-m value of 13.3 mu M. No significant difference was observed either bet ween in vivo and in vitro derived embryos or between grade 1 and grade 2 embryos for methionine uptake. The methionine and glycine uptake of a day 7 bovine was similar to that of a day 4 mouse blastocyst. This is rather low if we consider the relative cell numbers.