Changes in energy metabolism during the early development of Xenopus laevis.

Xenopus embryos at various development stages were incubated in the presence of labelled substrates and the 14CO2 production determined. From the rates of oxidation of glucose labelled in positions 1 and 6 and from that of radioactive acetate, pyruvate and glutamate, it was concluded that the Embden-Meyerhof pathway and the Krebs cycle are functional during early embryogenesis, but that their relative participation in the metabolic processes is limited and increases from gastrulation onwards. Early development is characterized by the predominance of the pentose cycle and the glutamate-aspartate cycle. Furthermore, it was shown that glutamate may be the main energy source up to gastrulation.