Glycogen Levels of Preimplantation Mouse Embryos Developing In Vitro

The glycogen content of mouse embryos developing in vitro has been estimated by an enzymatic technique. There were three periods of net glycogen synthesis in such embryos: (1) during development from day 1 postcoitum to day 2 postcoitum, (2) from day 2 postcoitum to day 3 postcoitum, and (3) from day 5 pOstcoitum to day 6 postcoitum (i.e., in blastocysts). Day 5 blastocysts contained 2.23 ng glycogen per embryo, increasing to 9.91 ng on day 6. However, deletion of glucose from the culture medium produced levels of 0.52 and 1.45 ng per blastocyst on days 5 and 6, respectively. Possible relationships between these findings and the role of glucose in the metabolism of the embryos are discussed.