Studies of mitochondrial energy systems during embryogenesis in the rat

Mitochondria isolated from rat embryos of Day 11 to Day 14 of gestation showed an equal capacity to carry out oxidative phosphorylation with P:O ratios of approximately 3 for pyruvate-malate and 2 for succinate as substrates. Activities of succinic dehydrogenase, cytochrome oxidase, and mitochondrial ATPase remained at nearly constant levels in the preparations during this period of gestation, but DPNH oxidase activity increased over 2-fold. The increase in DPNH oxidase activity could be prematurely induced at Day 11 of gestation of the embryos by prior treatment of the pregnant rats with an atmosphere containing 85% oxygen and 0.4% CO 2, but no changes in the growth and development of the treated embryos were found by gross examination.