Uptake and incorporation of glucose especially into the glycogen pools of preimplantation mouse embryos during culture in vitro.

Rate of [14C]glucose uptake by mouse embryos during in vitro culture in media containing optimal concentrations of lactate and pyruvate increased throughout preimplantation development. A reduction in the glucose concentration of the medium from 5.56 to 0.28 mM resulted in a two- to fivefold decrease in glucose metabolism, suggesting near-saturation of the membrane carrier at the lower concentration. Changes in the level of lactate and pyruvate in the medium had little effect on glucose metabolism after the third cleavage division. However, further evidence of interaction between energy substrates during the initial cleavage was obtained. Glucose was stored either as desmoglycogen during early cleavage or in a larger acid-soluble glycogen pool in the latter stages of development. The accumulation of glycogen calculated from its production by blastocysts cultured in either 5.56 or 0.28 mM glucose greatly exceeded that determined in blastocysts freshly collected from the uterus. The absence of lactate and pyruvate from the medium had only minimal effects on glycogen accumulation. Most of the glucose carbon was stored as a form of glycogen. However, considerable amounts were also found in acid-soluble material other than glycogen at all developmental stages, probably as the parent compound and its catabolites. Some was also present in lipids, nucleic acids and proteins.