Amino Acid Incorporation by Isolated Rat Liver Mitochondria during Liver Regeneration

Intact mitochondria, isolated from regenerating rat liver 2-3 days after partial hepatectomy, are 2.5-3 times more active in amino acid incorporation than mitochondria from control livers. Liver mitochondria from sham-operated animals showed normal amounts of incorporation. Sterile procedures insured low levels of bacterial contamination; cycloheximide was used to eliminate any contribution by contaminating microsomes. Mitochondria from control and 3-day-old regenerating livers were nearly identical in their concentration of several respiratory chain components, P/O ratios, specific O₂ consumption, and cytochrome c oxidase activities. Small differences were observed in respiratory control ratios but these were shown to be unrelated to the differences observed in amino acid incorporating ability. Differential contamination by lysosomes and differences in lysosome fragility were also shown not to be factors in the increased incorporation by regenerating liver mitochondria. Thus, mitochondria from rapidly growing and dividing mammalian tissues are more active in protein synthesis than mitochondria from tissues that grow and divide more slowly.