Tests of the ability of two-cell mouse embryos to utilize selected precursors of phosphoenolpyruvic acid and pyruvic acid

Phosphoenolpyruvic acid and pyruvic acid are among the few compounds that two‐cell mouse embryos have been found capable of using as energy sources; most of the compounds in the glycolytic pathway and Krebs cycle that have been tested have been found unusable. Because 3‐phosphoglyceric acid of the compound converted most directly to phosphoenolpyruvic acid in glycolysis, one objective of this study was to examine whether it could support development of two‐cell embryos as phosphoenolpyruvic acid can. An additional objective was to examine whether alanine or serine, two amino acids that in later stages of development are converted to pyruvic acid for entry into the Krebs cycle, could support development of two‐cell embryos as pyruvate does. Two‐cell embryos were obtained from the oviducts of mice (C57BL × CBA) and were cultured in medium that contained 3‐phosphoglyceric acid, alanine, or serine in lieu of the pyruvate, lactate, and glucose usually contained in the medium. The embryos failed to undergo cleavage but this was not attributable to only a single energy source having been provided; embryos developed in a medium that provided only pyruvate. The results suggest that mouse embryos at the two‐cell stage of development are either unable to transport 3‐phosphoglyceric acid, alanine, and/or serine or are unable to convert the compounds to chemically similar ones; phosphoenolpyruvic acid or pyruvic acid, which can be metabolized by two‐cell mouse embryos. The results offer additional evidence that compounds more than one step removed from pyruvate in metabolic pathways are not used by two‐cell mouse embryos and, furthermore, suggest that the embryos cannot use alanine even though it is but a single step removed from pyruvate. © 1993 wiley‐Liss, Inc.