BLASTOCOELE 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 rat s was determined by culturing morula stage embryos for 24 h in the pre sence of three inhibitors of ATP generation cyanide, antimycin-A and 2 ,4-dinitrophenol (DNP). Rat morulae could form blastocysts in concentr ations of cyanide that are toxic to the embryos of other mammals. Simi lar results were obtained with antimycin-A and DNP, although DNP reduc ed the number of blastocysts that formed. A non-invasive ultramicroflu orometric assay was used on single blastocysts and the glycolytic path way was shown to be stimulated in the presence of these inhibitors. Th ese results suggest that, uniquely among preimplantation embryos studi ed, the developing rat blastocyst does not have an absolute requiremen t for oxidative phosphorylation but may be able to compensate by incre asing the amount of glucose consumed and metabolized by glycolysis. Th is pattern of metabolism may be related to the changing maternal envir onment during development, with blastocoel cavity formation and implan tation taking place in increasingly anoxic conditions.