Increase In Hepatocyte Volume Research Articles

Polychlorinated biphenyl congener 153-induced ultrastructural alterations in rat liver: A quantitative study

Alterations in the liver of male and female Sprague-Dawley rats fed PCB congener 153 (2,2′,4,4′,5,5′-hexachlorobiphenyl) at 0.5, 5, or 50 ppm concentrations in diets for 13 weeks were determined morphometrically. A dose-dependent increase in hepatocyte volume was detected; the cytoplasmic compartment contributed to the increase in cell volume in an overwhelming fashion. Eighty percent and 250% increase in smooth endoplasmic reticulum volume and its surface area in hepatocytes were estimated in animals of both genders from 5- and 50-ppm groups, respectively; the organelle played the largest part in the increase in cytoplasmic volume. Rough endoplasmic reticulum alteration was shown to depend on gender, where the volume per hepatocyte was augmented by 40% and 45% in females of 5- and 50-ppm groups, respectively, however, 30% and 20% decreases in volume of this organelle were noted in males at those congener concentrations. A decrease of 13% in normal mitochondria volume at 50 ppm concentration was observed, which may have been a consequence of a transformation of these mitochondria to abnormal types. Two types of abnormal mitochondria, named Type I and Type II, were defined: the former comprised mitochondria that had cristae which laying parallel to the long axis of the organelle and the latter showed C- or ring-shaped profiles. Data analysis revealed a trend toward an increase in abnormal mitochondria volume in the cells as the congener concentration elevated. In addition, a threefold increase in the volume of lysosomal elements per hepatocyte was noted in 50 ppm PCB-fed rats of both genders. Also, a significant increase in peroxisome volume per cell in female rats was detected at a lower concentration than it was in the male. This study, which is a first ultrastructural quantitative investigation on the effects of a PCB that included many parameters. The methodology, and the data may prove useful to provide better understanding of pathology in the evaluation and regulation of toxic chemicals.

Administration of Escherichia coli endotoxin to rat increases liver mass and hepatocyte volume in vivo.

We have established, in vivo, an increase in liver mass and hepatocyte volume after a single intraperitoneal administration, to fasted rats, of Escherichia coli lipopolysaccharide (0127:B8) at 3 mg/kg. The phenomenon was time- and dose-dependent and could be prevented by treatment with polyclonal antiserum against tumour necrosis factor-alpha (TNF-alpha) before the endotoxin injection. Endotoxin caused an increase of 26% in the hepatic mass compared with fasted controls at 24 h. An increase of 27% in the hepatic water content underlay the altered hepatic mass which could not be accounted for by a change in the volume of hepatic blood and/or interstitial fluid (measured in vivo), suggesting an expansion in the hepatocellular volume. This is supported by an increase of 25% in the K+ content of the endotoxic livers. Morphometric study confirmed a 15% increase in hepatocyte volume after endotoxin administration. The data are discussed in the light of possible metabolic effects of increased hepatocyte volume.

Swelling-activated anion conductance in skate hepatocytes: regulation by cell Cl- and ATP.

Cell swelling activates an outwardly rectifying anion conductance in mammalian cells. The channel responsible for this conductance mediates volume-regulatory efflux of organic osmolytes such as taurine. We observed a similar conductance in hepatocytes from the skate Raja erinacea. Whole cell Cl- conductance was increased > 100-fold by a 2-fold increase in hepatocyte volume. The conductance was outwardly rectifying and had a relative cation permeability of approximately 0.2. Cation permeability was increased by reductions in patch pipette CsCl concentration, suggesting that the channel pore contains saturable anion and cation binding sites with different anion and cation affinities. The conductance had a broad anion selectivity and a relative taurine permeability of 0.17. Activation of the conductance required intracellular ATP or a nonhydrolyzable ATP analogue. Elevation of intracellular Cl- from 20 to 155 mM reduced current activation while the rate and extent of cell swelling were unaffected. Reduction of intracellular Cl- concentration to 5-10 mM caused spontaneous current activation without cell swelling. These results suggest that increases in cell Cl- levels increase the volume set point of the channel. We propose that the main function of the outwardly rectifying anion channel is nonselective transport of organic solutes.

Hepatocyte swelling stimulates macromolecular synthesis

In hepatocytes from fasted rats, several amino acids are known to stimulate glycogen synthesis via activation of glycogen synthase. The hypothesis that an increase in cell volume resulting from amino acid uptake may be involved in the stimulation of glycogen synthesis is supported by the following observations. 1) The extent of stimulation of glycogen synthesis by both metabolizable and nonmetabolizable amino acids was directly proportional to their ability to increase cell volume, except for proline, which stimulated glycogen synthesis more than could be accounted for by the increase in cell volume. 2) Both cell swelling and stimulation of glycogen synthesis by amino acids were prevented when hepatocytes were incubated in hyperosmotic media containing sucrose or raffinose. 3) Increasing the cell volume by incubating hepatocytes in Na+-depleted media in the absence of amino acids also stimulated glycogen synthesis. 4) Stimulation of glycogen synthesis by Na+ depletion was prevented by restoring the normal osmolarity with sucrose, but not with choline chloride which, by itself, stimulated glycogen synthesis and increased cell volume. It is concluded that stimulation of glycogen synthesis by amino acids is due, at least in part, to an increase in hepatocyte volume resulting from amino acid uptake, and that hepatocyte swelling per se stimulates glycogen synthesis.

Swelling of rat hepatocytes stimulates glycogen synthesis.

In hepatocytes from fasted rats, several amino acids are known to stimulate glycogen synthesis via activation of glycogen synthase. The hypothesis that an increase in cell volume resulting from amino acid uptake may be involved in the stimulation of glycogen synthesis is supported by the following observations. 1) The extent of stimulation of glycogen synthesis by both metabolizable and nonmetabolizable amino acids was directly proportional to their ability to increase cell volume, except for proline, which stimulated glycogen synthesis more than could be accounted for by the increase in cell volume. 2) Both cell swelling and stimulation of glycogen synthesis by amino acids were prevented when hepatocytes were incubated in hyperosmotic media containing sucrose or raffinose. 3) Increasing the cell volume by incubating hepatocytes in Na(+)-depleted media in the absence of amino acids also stimulated glycogen synthesis. 4) Stimulation of glycogen synthesis by Na+ depletion was prevented by restoring the normal osmolarity with sucrose, but not with choline chloride which, by itself, stimulated glycogen synthesis and increased the cell volume. It is concluded that stimulation of glycogen synthesis by amino acids is due, at least in part, to an increase in hepatocyte volume resulting from amino acid uptake, and that hepatocyte swelling per se stimulates glycogen synthesis.

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.

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.

Correlation between liver morphology and portal pressure in alcoholic liver disease.

In 14 alcoholic patients, the degree of hepatic architectural destruction was graded (preserved architecture; nodules alternating with preserved architecture; totally destroyed architecture) and related to portal pressure. A positive correlation was found between the degree of architectural destruction and both wedged hepatic vein pressure (r = 0.72, p less than 0.01) and wedged-to-free hepatic vein pressure (r = 0.67, p less than 0.02). Degree of fatty change, fibrosis, inflammation, necrosis and occurrence of Mallory bodies showed no correlation with portal pressure. After morphometrical evaluation of liver biopsies, no significant correlation was found between mean hepatocyte volume or relative sinusoidal vascular volume and portal pressure. To test whether an increase in hepatocyte volume compresses the vascular structures and causes portal hypertension, the ratio of relative sinusoidal vascular volume to mean hepatocyte volume, which expresses the compression of the vascular structures exerted by enlargement of hepatocytes, was related to portal pressure. No significant correlation was found. Further, mean hepatocyte volume was not significantly correlated to relative sinusoidal vascular volume. The present findings are in accordance with the hypothesis that elevated hepatic vascular resistance and portal pressure in alcoholic liver disease are in part determined by the severity of the hepatic architectural destruction and subsequent distorsion and compression of the efferent vein system. Parenchymal changes, including changes in hepatocyte volume, seem to be of minor importance.

On the characteristics of alcohol-induced liver enlargement and its possible hemodynamic consequences

Chronic consumption of alcohol leads to an increase in liver weight, primarily due to an increase in hepatocyte volume. About 50–60% of such an increase is due to an increase in intracellular water. Accumulation of intracellular K + osmotically accounts for about one half of the increase in intracellular water, while an increase in soluble proteins plays only a minor role in such an increase in cell volume. The increase in intracellular water is accompanied by a relative reduction in water in the extracellular space, probably due to compression of the extracellular volume by the enlarged hepatocytes. It is suggested that such an increase in hepatocyte size, with an attending reduction of the extracellular volume, results in an increased resistance to blood flow through the liver and thus in an increase in portal pressure. In alcoholics, portal and intrahepatic pressure correlate with cell size both in cirrhotics (r=0.79) and in non-cirrhotics (r=0.74), thus suggesting that cell enlargement plays a major role in the production of portal hypertension in the alcoholic.

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.

Liver biopsy and prognosis in acute liver failure.

Liver biopsy was performed in 38 patients with fulminant hepatitis and coma and repeated in 22. Stereological estimation of hepatocyte volume was correlated with levels of clotting factors. Early liver biopsy allowed prognosis in 55% of the cases. All patients with a hepatocyte volume of <35% and thromboplastin time </=10% died; all patients but two with hepatocyte volume >/=35% and thromboplastin time >10% recovered consciousness (n = 9) or at least showed evidence of marked liver regeneration (n = 2). On serial liver biopsy a significant increase in hepatocyte volume and clotting factors was only observed in patients who recovered consciousness. The estimated liver cell mass after regeneration in patients who recovered consciousness was >/=45% and <45% in the patients who did not.