Non-invasive measurement of nutrient uptake by single cultured pre-implantation mouse embryos

The uptake of pyruvate and glucose by single, cultured mouse embryos has been measured non-invasively throughout the pre-implantation period. The embryos, derived from CBA x C57F1 females and F1 males were removed from the oviducts on day 1 or day 2 following mating, and cultured to the blastocyst stage in M16 medium. Each day they were removed from culture and incubated in 20 nl medium M2 for 3 h. Serial approximately 0.5-nl samples were analysed for pyruvate and glucose by an ultramicrofluorescence technique. Pyruvate uptake exceeded that of glucose until the 8-cell/morula stage, when glucose consumption increased dramatically. The morphological development and patterns of nutrient uptake by embryos removed on day 2 resembled more closely those of freshly collected embryos than of embryos removed on day 1. These methods will enable the biochemistry of early embryos to be monitored non-invasively prior to transferring them into the uterus of recipient females.