Responses of fatty livers of mice of carbon tetrachloride

Peri- and postnatal development of heterogeneity in the amounts of endoplasmic reticulum in mouse hepatocytes

The surface density and area per cell of the endoplasmic reticulum (ER) in periportal and perihepatic hepatocytes from male ddY mice, "17-, 18-, and 19-day-old fetuses," "newborn and 1-, 5-, 10-, and 20-day-old animals," and "adult animals" were analyzed by quantitative electron microscopy. The surface density of rough ER was not significantly different between periportal and perihepatic cells in all age groups examined, except for 19-day-old fetuses in which the value was greater in periportal cells than perihepatic cells. The surface density of smooth ER and total (rough and smooth) ER did not significantly differ between the periportal and perihepatic cells from 17-day-old fetuses to 5-day-old animals. In 10- and 20-day-old and adult animals, the values of smooth and total ER were greater in perihepatic cells than in periportal cells. When the data were expressed as area per cell, the patterns of subacinar distributions hardly differed, but age-related changes differed considerably from the patterns seen in the surface density data. The differences were generally caused by the increase in hepatocyte volume between 20 days of age and adulthood, especially in perihepatic cells, and by the changes in volume during the perinatal period. The results show that differences in the surface density and area per cell of smooth and total ER between periportal and perihepatic hepatocytes evident in adult animals are not present in fetal and newborn animals but arise during postnatal development.

A functional and structural heterogeneity is formed among fetal rat hepatocytes during culture

Fetal rat hepatocytes (22-day-old, full-term) in vivo were homogeneous in ultrastructure and glucose 6-phosphatase (G6Pase) distribution throughout the liver acinus. These cells were isolated and cultured for 17 days in Williams medium E containing 10% fetal calf serum, dexamethasone, insulin, and glucagon. Heterogeneity among hepatocytes appeared progressively during culture. There were variations in numbers of binucleated cells, cytoplasmic ultrastructure (e.g., in the distribution of glycogen and the quantity of ultrastructure (e.g., in the distribution of glycogen and the quantity of mitochondria), and intensity of histochemical reactivity for G6Pase. The cells could be classified generally into two types: type I cells had some characteristics of periportal hepatocytes and type II cells those of centrolobular hepatocytes in in vivo adult liver. The results show that a functional and structural heterogeneity can be formed among fetal hepatocytes in monolayer culture without differences in supply of oxygen, nutrients, and hormones. A hidden heterogeneity might already exist among hepatocytes in full-term fetuses even though it cannot be detected ultrastructurally or cytochemically.

Development of morphologic heterogeneity of hepatocyte mitochondria in the mouse

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.

Development of ultrastructural heterogeneity among hepatocytes in the mouse

Ultrastructural stereological analyses of periportal and centrilobular hepatocytes of newborn, 5- and 10-day-old, and adult male ddY mice were carried out to study the postnatal development of the morphologic heterogeneity among hepatocytes. In newborn animals, the periportal and centrilobular cells did not differ in the volume densities of the smooth and rough endoplasmic reticulum; in the volume and numerical densities of the mitochondria, lysosomes, peroxisomes, and lipid droplets; or in the shape (the axial ratio) of the mitochondria. In 5-day-old animals, the volume densities of the mitochondria and rough endoplasmic reticulum were greater in periportal cells than centrilobular cells, and the volume density of the smooth endoplasmic reticulum was greater in centrilobular cells than periportal cells. In 10-day-old animals, a further difference was seen in the numerical density of the mitochondria, which was greater in centrilobular cells than periportal cells. Adult hepatocytes showed also a difference in the axial ratio of the mitochondria, which was greater in centrilobular than periportal cells; there was no difference in the volume density of the rough endoplasmic reticulum. When the data were expressed as volume and number per hepatocyte, the patterns of sublobular distributions of these organelles differed from the patterns seen in the volume and numerical density data, mainly in adult animals. This difference was caused by the marked increase in hepatocyte volume between 10 days of age and adulthood, especially in centrilobular cells. The results show that, in general, the ultrastructural heterogeneity among hepatocytes, evident in adult animals, is not present in newborn animals but arises during postnatal development, and suggest the occurrence of a lobular gradient in postnatal development of hepatocyte functions.

The heterogeneity of hepatocytes during the postnatal development of the mouse

Development of the hepatocyte heterogeneity was studied histochemically during the postnatal period. At birth ornithine carbamoyltransferase (OCT). succinate dehydrogenase (SDH) and NADH dehydrogenase (NADHDH) activities were evenly distributed throughout the liver acinus. Slightly uneven distribution within the acinus appeared at 3 days after birth in SDH and at 4 days after birth in OCT and NADHDH, changing to that of adult type at 10 or 12 days after birth which is characterized by a marked difference in the activities between zone 1 and 3. However, in animals of all age groups studied, glycogen was decreased mainly in zone 1 and 2 after 6 or 10 h of fasting and glucose 6-phosphatase activity was markedly reduced or disappeared in zone 3 and often in zone 2 after carbon tetrachloride administration. The results show that so-called "functional and structural heterogeneity among hepatocytes" consists of at least two different components, that formed gradually during the postnatal development and that existing already at birth.

Pesticide-induced changes in hepatic microsomal enzyme systems: further studies on the effects of 1,1,-di(p-chlorophenyl)-2-chloroethylene (DDMU) in the Japanese quail

Changes in the liver resulting from the low level dietary administration of 1,1-di(p-chlorophenyl)-2-chloroethylene (DDMU),p,p'-DDT, o,p'-DDT, p,p'-DDD and p,p'-DDE to Japanese Quail have been monitored. DDMU was exceptional in causing substantial increases in relative liver wt. and hepatic glucose-6-phosphatase after feeding at 100 ppm for 28 days. The time course of liver enzyme induction by DDMU has also been studied in Japanese Quail after periods of dietary administration ranging from 1--28 days with particular reference to changes in hepatic cytochrome P-450 and relative liver wt. Structural changes in the liver have been followed by reference to protein and lipid components. The hepatic response to DDMU appears to be biphasic. Initially there are substantial increases in hepatic cytochrome P-450 and relative liver wt., but the latter is largely due to accumulation of triglycerides. After approximately 20 days the level of hepatic cytochrome P-450 remain at a high 'plateau' level. This secondary phase of liver induction probably involves cell proliferation. It is concluded that DDMU causes major changes in the avian liver and either directly or through a metabolite causes pronounced microsomal enzyme induction.