NUTRIENT-UPTAKE AND CULTURE OF SMINTHOPSIS-MACROURA (STRIPE-FACED DUNNART) EMBRYOS

Glucose and pyruvate uptake by individual embryos were measured in a m arsupial species (stripe-faced dunnart) and a eutherian species (mouse ). At each stage of development, nutrient uptake by the dunnart embryo was around an order of magnitude greater than that of the mouse embry o. The pattern of glucose uptake by the dunnart embryo was not like th at for any eutherian embryo, all of which have a low glucose uptake be fore the blastocyst stage. Rather, in the dunnart embryo there was a s ignificant increase in glucose uptake after the third cleavage divisio n, increasing from 13.6 pmol embryo h(-1) at the 4-cell stage to 34.9 pmol embryo h(-1) by the 8-cell stage. This increase in glucose uptake before blastocyst formation may be attributed to an increased energy demand associated with the movement of cells within the dunnart embryo . Using a new culture system, it was possible to culture 66% of dunnar t embryos at the 2-4-cell stage and 80% of those at the 8-16-cell stag e to the unilaminar blastocyst stage. Embryos cultured from the 2-cell to the 4-cell stage were retarded by around 12 h when they reached th e blastocyst stage. Developmental retardation was also reflected in th e pattern of nutrient uptake, which lagged behind that of embryos deve loped in vivo. The present study has shown that it is possible to cult ure the early marsupial embryo to the blastocyst stage in a serum-free culture system, while concomitantly quantifying embryonic nutrient re quirements. Such an approach is essential for species where there is a paucity of material for study.