Effects of pyruvate and glucose on the development of human preimplantation embryos in vitro.

Although human embryos will develop in vitro for six days or more, little is known about the effects of the primary nutrients, pyruvate and glucose, on development. Because the nutrient requirements of embryos change throughout preimplantation development, the effects of altering substrate concentrations in the culture medium were examined, using 'surplus' human preimplantation embryos cultured from the two-four-cell stage to the blastocyst stage in medium containing various concentrations of pyruvate and glucose. Between the one-cell stage and the two-four-cell stage all of the embryos were exposed to 0.47 mmol pyruvate l-1 and 5.5 mmol glucose l-1. Pyruvate as sole substrate in the medium could support blastocyst development to an extent of 59% (10 of 17). Conversely, culture of embryos in pyruvate-free medium resulted in the developmental arrest of 84% (21 of 25) of embryos, and for the 16% (4 of 25) that did reach the blastocyst stage there was a significant decrease in metabolic activity on day 4-5, during the morula to blastocyst stage transition. Embryos could not use glucose to compensate for the lack of pyruvate in the medium. Pyruvate uptake was related to exogenous concentration and optimal development occurred at the highest concentration tested, 0.47 mmol l-1. Embryo development to the eight-cell stage was slightly enhanced 82% (14 of 17) versus 60% (24 of 40) when no glucose was added to the medium, and the resulting blastocysts had significantly more cells (99.1 +/- 13.5 versus 58.4 +/- 8.2; P < 0.02) than did embryos grown in the presence of 1 mmol glucose l-1.(ABSTRACT TRUNCATED AT 250 WORDS)