Observations on iron uptake, iron metabolism, cytochrome c content, cytochrome a content and cytochrome c-oxidase activity in regenerating rat liver

摘要

1. Differential and density-gradient centrifugation were used to fractionate mitochondria and fluffy layer from normal and regenerating rat liver. The iron, cytochrome a and cytochrome c contents and cytochrome c-oxidase activity were studied as well as the uptake of 59Fe into protein and cytochrome c. 2. A certain degree of heterogeneity was evident between the heavy-mitochondrial and light-mitochondrial fractions, and in their behaviour during liver regeneration. 3. The specific content of light-mitochondrial iron and cytochrome a was 1·3–1·4 times that of heavy mitochondria. Changes in cytochrome c-oxidase activity closely followed those of cytochrome a content during liver regeneration, but not for light mitochondria after 10 days. 4. Radioactive iron (59Fe) was most actively taken up by well-washed light mitochondria during early liver regeneration. After 22 days fluffy layer became preferentially labelled. This substantiates the view that fluffy layer partially represents broken-down mitochondria. 5. During early regeneration, light-mitochondrial fractions separated along a density gradient were about 3 times as radioactive, and showed distinct heterogeneity of 59Fe-labelling, in contrast with near homogeneity for heavy mitochondria. 6. Immediately after partial hepatectomy fractions corresponding to density 1·155 were 5–10 times as radioactive as particles of greater density. The radioactivity decreased sharply after 6 days. 7. These particles of low density possessed higher NADH–cytochrome c-reductase (1·5–5-fold) and succinate-dehydrogenase (1·1–2-fold) activities than typical mitochondrial fractions. Their succinate–cytochrome c-reductase and cytochrome c-oxidase activities were slightly lower. 8. The results are discussed in relation to mitochondrial morphogenesis, and a possible route from submitochondrial particles is suggested.