Development of structural heterogeneity of mitochondria in mouse hepatocytes

The volume and shape (the axial ratio:length/diameter) of mitochondria in periportal and perihepatic hepatocytes from newborn, 5 days old, 10 days old and adult male ddY mice were analysed by quantitative electron microscopy. In newborn animals, the volume and relative histogram of the axial ratio were not significantly different between periportal and perihepatic cells. Thereafter, the volume did not change significantly in periportal cells, whereas it decreased between 5 days of age and the adult in perihepatic cells. In adult animals, the volume in perihepatic cells was 26% of that in periportal cells. The relative histogram of the axial ratio for periportal cells deviated significantly to smaller values than in that for perihepatic cells in 5 days old, 10 days old and adult animals. Thus, the structural heterogeneity of hepatocyte mitochondria, evident in adult animals, is not present in newborn animals but arises during postnatal development.