Blastocoel cavity formation by preimplantation rat embryos in the presence of cyanide and other inhibitors of oxidative phosphorylation.

The role of oxidative phosphorylation in blastocoel development in rats was determined by culturing morula stage embryos for 24 h in the presence of three inhibitors of ATP generation: cyanide, antimycin-A and 2,4-dinitrophenol (DNP). Rat morulae could form blastocysts in concentrations of cyanide that are toxic to the embryos of other mammals. Similar results were obtained with antimycin-A and DNP, although DNP reduced the number of blastocysts that formed. A non-invasive ultramicrofluorometric assay was used on single blastocysts and the glycolytic pathway was shown to be stimulated in the presence of these inhibitors. These results suggest that, uniquely among preimplantation embryos studied, the developing rat blastocyst does not have an absolute requirement for oxidative phosphorylation but may be able to compensate by increasing the amount of glucose consumed and metabolized by glycolysis. This pattern of metabolism may be related to the changing maternal environment during development, with blastocoel cavity formation and implantation taking place in increasingly anoxic conditions.