ATP metabolism in cleavage-staged mouse embryos

Total ATP, ATP/ADP ratios, the rates of synthesis and turnover of ATP, and the level of cyanide inhibition of ATP synthesis were determined for 2-cell, 4-cell, 8-cell, late-morula and late-blastocyst mouse embryos. The results show that from the 2-cell stage to the late-blastocyst stage there are progressive decreases in total ATP and in the ATP/ADP ratios. These are accompanied by increases in the rates of ATP turnover as well as in the percentage of inhibition of ATP synthesis by cyanide. These data are discussed in relation to results from other metabolic studies on mouse cleavage-staged embryos and from studies describing configurational changes in the ultrastructure of mitochondria at these developmental stages. It is postulated that the mitochondrial ultrastructural changes during cleavage reflect differences in the levels of oxidative phosphorylation during specific metabolic steady states.