Glucose, pyruvate, and lactate concentrations in the blastocoel cavity of rat and mouse embryos

The concentrations of glucose, pyruvate, and lactate have been measured in the blastocoel fluid of single rat and mouse blastocysts, using the technique of micropuncture combined with an ultramicrofluorescence assay. When cultured in the presence of 5.55 mM glucose, 11.5-12.5 mM L-lactate and 0.25-0.33 mM pyruvate, concentrations in the blastocoel fluid of mouse and rat were 2.30 and 2.75 mM glucose, 14.6 and 19.6 mM L-lactate, and 0.13 and 0.50 mM pyruvate, respectively. When cultured in the presence of 1.0 mM glucose and 1.0 mM L-lactate, concentrations in the blastocoel fluid were 0.50 and 0.59 mM glucose and 2.22 and 3.70 mM L-lactate, respectively. These results suggest that (1) the blastocyst is capable of maintaining considerable concentration gradients of substrates across the trophectoderm, (2) the microenvironment of the blastocoel is adequately supplied with energy substrates for the development of the inner cell mass, and (3) the inner cell mass is capable of developing in both high and low glucose and lactate concentrations.