Increased span of oxido-reduction states between pyridine nucleotide and cytochrome c oxidase in the regenerating rabbit liver as measured by arterial ketone body ratio and near-infrared spectroscopy.

Oxido-reduction states of intramitochondrial pyridine nucleotide and cytochrome c oxidase and oxygen saturation of hemoglobin in the regenerating rabbit liver were studied with arterial ketone body ratio and tissue near-infrared spectroscopy. Arterial ketone body ratio (acetoacetate/beta-hydroxybutyrate), which reflects the oxido-reduction states of the intramitochondrial pyridine nucleotide (NAD+/NADH), was reduced from the control value of 0.93 +/- 0.09 to 0.42 +/- 0.03 12 h after 70% hepatectomy, while the oxido-reduction states of cytochrome c oxidase and the oxygen saturation of hemoglobin did not change. The velocity of ATP synthesis, as measured by state 3 respiration and ADP/O ratio in isolated mitochondria, increased by 61.4% 24 h after hepatectomy. These results support the near-equilibrium theory that an increased span in oxido-reduction state between pyridine nucleotide and cytochrome c oxidase drives mitochondrial ATP synthesis.