The effect of various possible energy sources on the development in vitro of two-cell mouse ova into blastocysts was examined. Energy for development of two-cell mouse ova could be supplied by lactate, pyruvate, oxaloacetate, or phosphoenolpyruvate. Compounds such as glucose, fructose, ribose, glucose-6-phosphate, fructose-1, 6-phosphate, acetate, citrate, α-ketoglutarate, succinate, fumarate, and malate could not provide energy for development of two-cell mouse ova. The optimum concentrations at pH 7.38 for those compounds which would supply energy was 5.00 × 10−2 M lactate, 3.16 × 10−4 M pyruvate, 3.16 × 10−4 M oxaloacetate, and 1.00 × 10−2 M phosphoenolpyruvate.
The possibility that interactions existed between the effects of osmolarity, pH, and energy source was examined in several experiments. There was no interaction between the effects of osmolarity and pH or osmolarity and the four possible energy sources. However, there was a significant interaction between energy source and pH. The result of this is that an increase in pH of the medium results in an increase in the optimum concentration of the compound supplying energy to the developing ova.