Development of morphologic heterogeneity of hepatocyte mitochondria in the mouse

Abstract

The ultrastructure of mitochondria in periportal and perihepatic hepatocytes from newborn, 5-, 10-, and 20-day-old, and adult male ddY mice was analyzed by quantitative electron microscopy. In newborn and 5- and 10-day-old animals, the axial ratio (length per diameter), surface to volume ratio (area of the outer membrane per unit mitochondrial volume), and volume density were not significantly different between periportal and perihepatic cells. In 20-day-old and adult animals, the surface to volume ratio was greater in perihepatic cells than periportal cells, and the volume density was greater in periportal cells than perihepatic cells. The axial ratio became greater in perihepatic cells than periportal cells in adult animals. However, there were no differences in the surface density of the outer membrane, and of the inner membrane and cristae between the cells of both zones in all age groups examined. When the data were expressed as volume and area per cell, the patterns of subacinar distribution and age-related changes differed from the patterns seen in the volume and surface density data mainly in adult animals. This difference was generally caused by the marked increase in hepatocyte volume between 20 days of age and adulthood, especially in perihepatic cells. The results show that differences between mitochondria in periportal cells and those in perihepatic cells in the shape (the axial and surface to volume ratios), volume density, and area of the outer membrane per cell, evident in adult animals, are not present in newborn animals but arise during postnatal development.

Fine structure and function of hepatocytes during development

“…Thus functional heterogeneity is also evident in hepatocytes during this period. After weaning, the hepatocyte volume increases markedly, especially in the perivenular zone (Asada-Kubota et al, 1982;Kanai et al, 1986a;Kanamura et al, 1984aKanamura et al, ,b, 1985 (Fig. 1).…”

“…Considerable quantative data on postnatal development of hepatocyte ultrastructure have resulted from studies conducted without consideration of intralobular heterogeneity of cell structure andlor function. However, several recent studies have considered this important variable in quantitative analyses of the fine structure of mouse hepatocytes during development (Asada-Kubota et al, 1982;Kanai et al, l984,1986a,b;Kanamura et al, 1984aKanamura et al, ,b, 1985. Between birth and 10 days of age, the volume density of mitochondrial matrix, the surface density of mitochondrial inner membrane and cristae, and the volume density of peroxisomes increase in both periportal and perivenular hepatocytes (Asada-Kubota et al, 1982;Kanamura et al, 1985) (Figs.…”

“…Succinate dehydrogenase activity is localized to the inner membrane and cristae and is evenly distributed throughout the liver lobule in neonatal mice, but the activity increases to a greater extent in the periportal zone than in the perivenular zone during the postnatal period (Kanamura and Asada-Kubota, 1980). Therefore, the developmental pattern of succinate dehydrogenase distribution within the lobule does not correspond to that of the area of inner membrane and cristae (Kanamura et al, 1984a(Kanamura et al, , 1985 (Fig. 9).…”

“…One reason for these apparent discrepancies is that no distinction was made between periportal and perivenular hepatocytes in these studies. Kanamura et al (1984aKanamura et al ( ,b, 1985 analyzed the development of mitochondrial ultrastructure in hepatocytes from the periportal and perivenular zones in the mouse. The volume of mitochondria or mitochondrial matrix per unit cytoplasmic volume increases between birth and 10 days of age in both periportal and perivenular hepatocytes.…”

Liver Architecture

“…They vary in size and shape and make up about 20% of the cytoplasmic volume. According to investigations in mice, the structural het erogeneity of hepatocyte mitochondria is not present in newborn animals but arises during postnatal development [27], In the rat liver, the mitochondria are on average shorter and larger at the beginning of the sinusoid and become progressively longer and thinner to ward its end. The mean volume of mitochon dria in the periportal cells is more than dou ble that of perivenous mitochondria [28], Hepatic lysosomes are cytoplasmic parti cles surrounded by a membrane that is [22], Partial hepatectomy or toxic injury causes the remaining cells to proliferate much faster.…”