Carbon dioxide and lactate production from [14C]glucose were measured for post-implantation mouse embryos aged 6 to 9½ days post coitum in static cultures with a defined medium. The rate of metabolism increased rapidly and paralleled the increase in protein content indicating a fairly uniform rate of metabolism throughout the period. At all stages studied more than 90% of the glucose utilized was converted to lactate. Over a quarter of carbon dioxide produced was derived from the C-1 position resulting in high C-1: C-6 ratios, indicating that the Pentose Phosphate Shunt is a major oxidative pathway.
The influence of various culture condition on CO2 production showed that high concentrations of glucose did not affect glucose utilization whilst high lactate concentrations had a significant inhibitory effect. Pyruvate had no discernible effect.