The alterations of sinusoidal endothelial fenestration (SEF) were elucidated in rats liver acutely or chronically fed ethanol and after withdrawal of ethanol administration using scanning electron microscope. The liver sinusoids were perfused at 10 cmH2O pressure via portal vein and diameter, number and porosity of SEF were analysed morphometrically. There was heterogeneity in size and number of SEF in the hepatic lobule in control rats. In control rats, the diameter of SEF in zone 1 was significantly (p<0.001) larger than that in zone 3 and the number was significantly (p<0.001) more in zone 3 compared with zone 1. The porosity of zone 3 compared with zone 1 was significantly (p<0.05) larger. Chronic ethanol consumption led to significant enlargement (p<0.001) of diameter, decrease (p<0.001) in number and increase (p<0.01) in porosity in zone 3 compared with control. After withdrawal of ethanol administration these changes recovered to the control levels. The present results indicate that the alterations of SEF may play a role in the pathogenesis of alcoholic liver injury.
The cytoskeletons of hepatocytes and biliary epithelial cells in bile duct ligated rate livers were investigated by transmission and scanning electron microscopy. The three dimensional organization of the intermediate filaments (IFs) of hepatocytes and biliary epithelial cells was clearly demonstrated by scanning electron microscopy. Cell borders and dilated bile canaliculi were well preserved after perfusion with detergent solution. A very dense filamentous network of IFs was seen throughout the cytoplasm, especially around the dilated bile canaliculi and at the cell borders. IFs in biliary epithelial cells were more numerous compared with hepatocytes. Morphometric analysis showed that the IFs of hepatocytes significantly (p greater than 0.001) increased in amount in bile duct ligated rats. The IFs of biliary epithelial cells showed no significant changes in bile duct ligated rats compared to controls. These results suggest that the increase in IFs in hepatocytes results from the adaptation of the hepatocytes to the stress imposed by bile duct ligation. It may be that the resulting intracanalicular pressure and back diffusion of bile induces a metaplastic change in hepatocytes so that they acquire more IFs to function like the bile duct epithelium to conduct bile flow.
The immunoelectron microscopic localization of actin in hepatocytes was studied in normal, common bile duct-ligated, and phalloidin treated rats. We used the low temperature embedding procedure with Lowicryl K4M and protein A-gold technique was applied to demonstrate the localization of actin. The tissues embedded in Lowicryl K4M at low temperature provided good preservation of ultrastructure and antigenicity of actin. In control rats bile canaliculi were clearly visualized and most of the gold particles were observed on the bile canalicular microvilli, at the pericanalicular ectoplasm, at the cell border, and on the sinusoidal microvilli. In common bile duct-ligated rats and phalloidin treated rats, pericanalicular ectoplasm was thickened and many gold particles were seen there.
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