Effect of agents which rearrange the cytoskeleton in vitro on the structure and function of hepatocytic canaliculi

The integrity of the cytoskeletal structure of the bile canaliculus (BC) may be necessary for bile secretion. This includes actin filaments in microvilli, cytokeratins in the pericanalicular sheath and microtubules in the surrounding cytoplasm. We studied these cytoskeletal structures and also the secretory function of the hepatocytes in tissue culture using double-label fluorescent staining and the transhepatic transport and secretion of fluorescein diacetate and horseradish peroxidase. The hepatocytes were obtained from 14-day-old male rats. They were cultured in serum-free Williams's E medium, with insulin and dexamethasone added to induce differentiation. Four treatment groups of hepatocytes were studied: (a) colchicine (10(-4)M for 1 hour), (b) cytochalasin B (4 micrograms/ml for 1 hour), (c) ethanol (30 to 90 mM for 24 hours) and (d) controls. Colchicine caused the disappearance of the microtubules and completely inhibited the secretion of fluorescein diacetate and horseradish peroxidase into the BC. It did not affect the uptake or transport of fluorescein diacetate on horseradish peroxidase to the BC. Cytochalasin B disrupted the actin filaments and caused their aggregation around the BC. The canaliculi were dilated and the microvilli were decreased but the secretion was normal. Ethanol did not affect either the structure of the cytoskeleton or inhibit secretion. It is concluded that the secretory function of the BC requires the integrity of microtubules in cultured hepatocytes. The integrity of actin is not necessary for uptake, transport, or secretion as long as the pericanalicular sheath remains intact. Ethanol had no effect on the structure or the function of the cytoskeleton of the bile secretory apparatus.

[A further study of capillary-like bile ductule proliferation in chronic active hepatitis]

64 cases of chronic active hepatitis (CAH) and 84 cases of other chronic liver diseases were studied with keratin antibody immunohistochemistry. Proliferation of capillary-like bile ductules (CLBD) was more remarkable in the former cases than that in the latter cases with positive keratin reaction in the cytoplasm. Therefore, proliferation of CLBD was considered to be a characteristic lesion of CAH, which might be used as one of the criteria for differential diagnosis of CAH. This paper also reports the ultrastructural appearance of CLBD in detail and the result of HBV DNA in situ hybridization for CLBD, suggesting that HBV might infect CLBD.

Histologic and scanning electron microscopic observations of intrahepatic peribiliary glands in normal human livers

The three-dimensional configuration of the intrahepatic peribiliary glandular system was examined in normal autopsied livers by scanning electron microscopic observations of the intrahepatic biliary tract casts. Biliary tract casts were made by injection of resin into the biliary tree and subsequent corrosion of the hepatic parenchyma. There were many projections on the surface of the biliary casts and they could be morphologically classified into pouchlike and treelike projections. These projections tended to be arranged on opposite sides of the biliary casts. The treelike projections from the large bile ducts at the bifurcation frequently anastomosed each other. By comparing the findings of biliary casts with histologic findings as well as the measuring of these projections and thickness of bile duct wall, it was suggested that the treelike projections correspond to the extramural peribiliary glands and the pouchlike ones to the intramural ones, both of which are normally present around the intrahepatic biliary tree. Thus, it was suggested stereologically in this study that substance(s) produced in the intrahepatic peribiliary glands may be secreted into the bile ductal lumen and thereby participate in the modification of bile composition.

Quantitative assessment of canalicular bile formation in isolated hepatocyte couplets using microscopic optical planimetry

Isolated rat hepatocyte couplets (IRHC) are primary units of bile secretion that accumulate fluid in an enclosed canalicular space with time in culture. We have quantitated the rate of canalicular secretion in IRHC cultured for 4-8 h by measuring the change in canalicular space volume by video-microscopic optical planimetry using high resolution Nomarski optics. Electron microscopic morphometric studies revealed significant increases in canalicular membrane area after 4-6 h in culture. Canalicular secretion in basal L-15 medium (3.8 +/- 1.3 fl/min) increased significantly with the choleretic bile salts (10 microM), taurocholate, and ursodeoxycholate (14 +/- 7 fl/min each). Secretion rates after exposure to bile acids correlated directly with the canalicular surface area before stimulation. In contrast, expansion times after stimulation varied inversely with initial canalicular volumes. Ursodeoxycholic acid failed to produce a hypercholeresis at 10-, 100-, or 200-microM concentrations compared with taurocholate, either in normal or taurine-depleted IRHC. The present findings establish that rates of canalicular bile secretion can be quantitated in IRHC by serial optical planimetry, both in the basal state and after stimulation with bile acids. Furthermore, ursodeoxycholate does not acutely induce hypercholeresis at the canalicular level in this model. Rather, both taurocholic and ursodeoxycholic acids induced secretion in proportion to the surface area of the canalicular membrane. The IRHC are a useful model to identify canalicular choleretics and for studies of canalicular bile formation.

Isolation of cell-to-cell adherens junctions from rat liver

A new isolation procedure for cell-to-cell adherens junctions has been developed using rat liver. From the bile canaliculi-enriched fraction obtained by homogenization of the liver and sucrose gradient centrifugation, the fraction rich in adherens junction was recovered by detergent treatment followed by sucrose gradient centrifugation. Light and electron microscopy revealed that this final fraction was mainly composed of the belt-like adherens junctions with their associated short actin filaments. Biochemical and immunological analyses have shown that vinculin is highly enriched in this fraction. Considering that vinculin is known to be localized in the cell-to-cell adherens junctions, we can conclude that we have succeeded in isolating the cell-to-cell adherens junctions. Furthermore, the constituents of the undercoat (dense layer underlying the membrane) of adherens junctions were selectively extracted from the fraction rich in junctions. Upon SDS electrophoresis of this extract, 10 polypeptides including vinculin, alpha-actinin, and actin were dominant. The results obtained are discussed with special reference to the molecular organization of the undercoats of cell-to-cell adherens junctions.

Bile secretory apparatus in the newborn dog: relationship between structural and functional immaturities

In the dog, bile secretion is not fully mature at birth and develops during postnatal life. To try to establish morphologic correlates to the physiologic deficiencies, we examined the ultrastructure of hepatic parenchyma and biliary epithelium in a newborn puppy and in 3 puppies of 1, 3, and 7 days of age. At birth, the hepatocytes contain much glycogen and fat droplets, a small smooth endoplasmic reticulum and Golgi apparatus, rare autophagic vacuoles, and numerous lysosomes. The sinusoidal microvilli are short, and submembrane vesicles are few and small. The bile canaliculus is not dilated, but few and short microvilli and no pericanalicular vesicles are seen. The biliary epithelial cells are normal in size, but the luminal surface of the bile ductule has no microvilli and numerous blebs. These morphologic features change with maturation and, by the first week of life, the fine structure of the hepatocytes, bile ductular cells, and biliary passages resemble that observed in the adult liver. These findings provide morphologic support for the concept that, in the dog, the bile secretory apparatus is immature at birth and develops during postnatal life.

Mucinous biliary papillomatosis: a tumour in need of wider recognition

We report three cases of mucinous biliary papillomatosis occurring high in the extrahepatic bile ducts. Histological assessment of malignancy is difficult and subjective because there is no unequivocal evidence of stromal invasion. Using anti-laminin antibodies to assess the basement membranes of these tumours we have found a large number of discontinuities in the epithelial basement membrane. On this basis we consider that mucinous biliary papillomatosis should be considered a low-grade malignancy. This would correlate with the natural history of these tumours, namely recurrence but with no widespread metastasis, death resulting from liver failure usually with 5-6 years of presentation.

Light and electron microscopic study of the liver in paraquat poisoning

Intrahepatic cholestasis in paraquat poisoning in man has been thought to be secondary to extensive bile duct injuries, though its exact mechanism remains unsettled. We have examined liver biopsy specimens from two cases of paraquat poisoning. Case 1 (fatal) presented severe intrahepatic jaundice, and liver biopsy showed centrilobular cholestasis with extensive bile duct loss. Ultrastructurally, dilatation of bile canaliculi with decrease of microvilli and thickening of pericanalicular ectoplasm was found in the hepatocytes. Case 2 (alive) showed mild liver dysfunction without jaundice. While liver biopsy showed nonspecific reactive changes with intact bile ducts and ductules, electron microscopy disclosed dilatation of bile canaliculi with decrease of microvilli and thickening of pericanalicular ectoplasm in the hepatocytes, suggesting that damage to the bile secretory apparatus in the hepatocytes develops irrespective of extensive bile duct loss. These findings suggest that bile secretory apparatus in the hepatocytes as well as biliary epithelial cells could be a target of paraquat or its metabolites.

Secretin empties bile duct cell cytoplasm of vesicles when it initiates ductular HCO3- secretion in the pig

To determine whether secretin has any effect on bile duct cell ultrastructure, bile duct cells from liver biopsy specimens of pigs were analyzed morphometrically. During secretory rest, bile duct cell cytoplasmic vesicles totaled 96 (84-103) arbitrary units per cell volume (U). Secretin increased bile HCO3- secretion from 9 mumol/min (range 6-15) to 131 mumol/min (range 118-200) and lowered the bile duct cell vesicles to 5 U (range 3-9). Acute elevation of arterial PCO2 to 10.9 kPa (range 10.2-11.1) doubled vesicle number in resting duct cells and augmented the secretory response to secretin. At high arterial PCO2, secretin cleared the duct cell cytoplasm of vesicles and more than doubled the basolateral plasma membrane surface area. Taurocholate-induced canalicular choleresis, in contrast, did not alter duct cell morphology. It is concluded that secretin clears the bile duct cell cytoplasm of vesicles as it initiates ductular HCO3- secretion, possibly through causing exocytotic insertion of vesicle material into the basolateral plasma membrane.

Intermediate filaments of hepatocytes and biliary epithelial cells in bile duct obstruction: transmission and scanning electron microscopy study

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.

Phalloidin-induced alterations of bile canaliculi

Phalloidin, a toxin from the plant Amanita phalloides, irreversibly polymerizes actin filaments and causes cholestasis. Three-dimensional structural changes induced by phalloidin in the bile canaliculi and the intra-acinar localization of these changes were studied in the rat liver by scanning and transmission electron microscopy. After 3 days of treatment, canalicular changes appeared mainly in zones 2 and 3 of Rappaport's acinus, but after 7 days of treatment changes occurred in bile canaliculi of the whole acinus. The changes in the bile canaliculi included tortuosity, saccular dilatation, loss of microvilli, bleb formation and elongation of canalicular side branches. Some side branches extended near to Disse's space, leaving only a thin cytoplasmic rim between the canalicular lumen and Disse's space. Kupffer cells were occasionally situated near such extended bile canaliculi and protruded their processes into the hepatic cord. These results suggest that bile canaliculi in zone 3 are more susceptible to phalloidin toxicity than those in zone 1 and that biliary constituents may leak from such altered bile canaliculi.

Pathologic changes in the cytokeratin pericanalicular sheath in experimental cholestasis and alcoholic fatty liver

The architectural framework of the pericanalicular sheath composed of cytokeratin intermediate filaments (IFs) was examined after phalloidin treatment, bile duct ligation, and alcoholic fatty liver in rats to assess the role of IFs in experimental cholestasis. Electron microscopy examination of whole mount unembedded extracted liver slices was employed to visualize the cytoskeleton. Immunofluorescence staining and immunoelectron microscopy of the sheath were also performed using monoclonal antibodies to rat hepatocyte cytokeratins CK49 and CK55. The thickness of the wall and the diameter of the lumens were measured. In the phalloidin-treated rats, the pericanalicular sheath was markedly dilated and thickened. Immunofluorescence staining showed that the CK49 and CK55 IFs were localized in the pericanalicular region, particularly in the pericentral area. Immunoelectron microscopy documented that the IFs at the thickened pericanalicular sheath consisted of both CK49 and CK55, which means that the thickening of the bile canaliculus was in part due to an increase of IFs and not just due to an increase in actin filaments. In the livers where the bile duct was ligated, the pericanalicular sheath was irregularly dilated and some parts of the sheath appeared thinned out or missing. The belt desmosome also appeared absent focally in the pericanalicular sheath. Immunofluorescence studies showed that the staining for CK49 and CK55 was reduced focally in the pericanalicular region. The CK55 antibody stained the cytoplasm of hepatocytes in the periportal area more intensely when compared with the controls. These results indicated that the pericanalicular sheath and the belt desmosome were focally disrupted in response to extrahepatic bile duct obstruction. In the ethanol-fed rats, the pericanalicular sheath was dilated, thickened and tortuous, and appeared focally flattened by large fat droplets. IFs in the cytoplasm were pushed to the cell periphery and were compressed against each other by the fat droplets. CK55 and CK49 appeared increased as indicated by the observed immunofluorescence at the pericanalicular region. Immunoelectron microscopy showed that IFs of the thickened pericanalicular sheath were composed of CK55 and CK49. It is suggested that the pericanalicular sheath functions to mechanically provide a scaffolding for the bile canaliculus which is vulnerable to the different forces involved in cholestasis of different pathogenesis such as focal compression and distortion by fat, hypertrophy in response to increased F actin and focal destruction by increased intracanalicular pressure.

Histological changes of bile duct in experimental graft-versus-host disease across minor histocompatibility barriers. II. Electron microscopic observations

Electron microscopic features of intrahepatic bile ducts of experimental mouse graft-versus-host disease (GVHD) across minor histocompatibility barriers were studied for 14 months after transplantation. In GVHD mice, the bile duct epithelial layer was consistently infiltrated by lymphoid cells and often accompanied by polymorphonuclear leukocytes, monocytes and rarely by plasma cells. The epithelial cells in close contact with and in the vicinity of these infiltrated cells showed a variety of degenerative changes, including darkness of the cytoplasm and the nucleus with shrunken, irregular contours, increase in the amount of endoplasmic reticulum and number of mitochondria, and formation of intracytoplasmic vesicles and diverticula, cytoplasmic blebs, and apoptopic bodies. Lymphocytes were in close contact with epithelial cells through a number of point-contacts and located in the lateral intercellular spaces and/or between the basement membranes and the epithelial cells. The localization of infiltrating lymphocytes beneath the epithelial cells with conspicuous detachment from the basement membranes strongly suggested a link with subsequent epithelial cell injury and death. The lymphoid cells had irregular cytoplasmic projections which occasionally extended into spaces created by retractions of the epithelial cell membranes, reflecting an activation of the lymphocytes. These findings support the notion that the bile duct lesions in GVHD across minor histocompatibility barriers are mediated by specifically sensitized lymphocytes against epithelial cell membrane antigens. From our previous finding that a large majority of the infiltrating lymphocytes had a phenotype of helper/inducer T cells, a putative role of these lymphocytes in the induction of the bile duct lesions is discussed.

Bile ductal and ductular changes of the livers in the renal allografted patients

Nine liver biopsies from six renal allografted patients suffering from liver injury were examined by light and electron microscope and immunostaining. The patients had never been on liver dysfunction prior to renal transplantation and after renal transplantation had been administered azathioprine continuously. These patients had shown HBs antigen negative sera. Three of these patients restored normal liver function after withdrawal of azathioprine. Accordingly, the liver diseases of the three were supposedly caused by azathioprine. The liver biopsies of six patients were histologically diagnosed as follows: chronic active hepatitis with severe cholestasis (1 patient), liver cirrhosis with cholestasis (1 patient), acute hepatitis (1 patient), and mild hepatitis (3 patients). The common pathological findings of six patients were degeneration of interlobular bile ducts and ductules, as well as degeneration of liver cells, and mild to moderate inflammatory cell infiltration of portal tracts and sinusoids. The degeneration of bile ductal and ductular cells were classified into two types: light microscopical finding showed vacuolar or eosinophilic cytoplasm and electron microscopic compatible findings showed hydropic cytoplasm scant of free ribosome and organelles, or dense cytoplasm rich in free ribosome and degenerated organelles. The basement membranes of interlobular bile ducts and ductules were always preserved.

Ultrastructural localization of type IV collagen, laminin and prolyl hydroxylase in biliary epithelial cells of rat liver following ligation of the common bile duct

Type IV collagen and laminin are major components of basement membrane (BM), whereas prolyl hydroxylase (PH) is a key enzyme in the hydroxylation of proline to hydroxyproline in collagen synthesis. In order to elucidate the exact mechanism of the formation of BM, immune electron microscopic observation of type IV collagen, laminin and PH was made in rat liver with marked proliferation of bile ducts following ligation of the common bile duct. Extracellular localization of type IV collagen was found in the BM of bile ducts and blood vessels and in the space of Disse in both normal rat liver and the liver of rats undergoing operation. Type IV collagen was localized in lamina rara and lamina densa. Laminin was codistributed with type IV collagen in BM but rarely in the space of Disse even in the liver of rats undergoing operation. Immunostaining of laminin was diffusely spread in lamina densa, but sparsely in lamina rara. Though no reaction products of type IV collagen and laminin were detected in the cytoplasm of normal biliary epithelial cells, they were found in rough endoplasmic reticulum (rER) and the vesicles close to the basal surfaces of the plasma membrane of the proliferating biliary epithelial cells. No evident localization of these components in Golgi apparatus was found. PH was found in rER of the biliary epithelial cells, hepatocytes, endothelial cells of vessels, fibroblasts and perisinusoidal cells except for Kupffer cells in normal rat liver. More intense and diffuse staining of PH was observed in rER in the proliferating biliary epithelial cells of the liver of rats undergoing operation in concomitance with the evident localization of type IV collagen in this organelle. These findings suggest that the major components of BM, such as type IV collagen and laminin in the proliferating biliary epithelial cells, are produced in rER and secreted by vesicles to the basal extracellular spaces, thus forming new BM in these circumstances.

An improved method for observing the cytoskeleton around the bile canaliculi of rat hepatocytes

In order to know more about the cytoskeletal structure around the bile canaliculi of hepatocytes, we used the following procedure. Liver specimens were passed through an 18-, a 21- and then a 23-gauge needle, by which they turned into cylindrical or oval blocks of 0.4 mm in diameter. Because of their small size, the cytosolic ground substances of every hepatocyte were washed out clearly after subsequent treatment with the solution containing 0.5% Triton X-100 and 0.5 mg/ml saponin for 15 min. This short-term extraction preserved both the cytoskeleton and the plasma membrane of the hypatocyte quite well, and we could observe the crossbridge filaments connecting between a core bundle of microfilaments and plasma membrane of the microvilli of the bile canaliculi.

Histological and ultrastructural examination of the intrahepatic biliary tree in primary sclerosing cholangitis

Intrahepatic bile ducts were examined histologically and ultrastructurally in wedge-biopsied liver specimens from three patients with primary sclerosing cholangitis. Bile ducts with periductal concentric fibrosis, which is a characteristic finding in primary sclerosing cholangitis, revealed ultrastructurally finger-like projections or fine undulations of the basal free surfaces with markedly duplicated basal lamina. The lamina was collared by a layer of elongated fibroblasts and thickened bundles of collagen fibers outwards. These changes were consistently found in all sizes of ducts examined, and might be related to progressive periductal fibrosis. Serial section observations showed that some severely affected ducts actually disappeared when accompanying severe periductal fibrosis. It would therefore appear that progressive periductal fibrosis may interrupt fluid and nutrient exchange between the bile duct epithelia and peribiliary capillary plexus, followed by obliteration of the biliary lumina. Although the bile ducts showed segmentally periductal lymphocytic infiltration and, ultrastructurally, point contacts between infiltrating lymphocytes and biliary epithelial cells were observed occasionally, the exact role of infiltrating lymphocytes in the pathogenesis of primary sclerosing cholangitis remains unclear.

[Unusual structure of the biliary system in the liver of the grass carp and the silver carp]

It is known that the bile canaliculus in the liver of almost all vertebrates is made up of membranes of two or more adjacent liver cells. Studying the liver cell ultrastructure of lasting and fed grass carp and silver carp, it was demonstrated that a bile canaliculus is formed by deep invagination of a cell membrane of one hepatocyte. The membrane forms microvilli along the bile canaliculus. The bile canaliculus is seen in the centre of liver cell cytoplasm on the cross section and stretches from the centre of the liver cell cytoplasm to the cell membrane on the longitudinal section. The bile canaliculus is connected with a small duct cell, which is distinct from a liver cell in its small size, little amount of cell organelles and the presence of cytoplasmic filaments. The terminal part of the biliary tract consists of one liver cell and one bile duct cell. The part of the tract adjacent to the terminal one is composed of two or three small bile duct cells devoid of basal membrane. Thus, the liver parenchyma is constituted of a net of numerous bile ducts. In the portal tract, there is a large bile duct, consisting of 12-13 bile duct cells, surrounded by basal membrane and connective tissue cells.

Nonsyndromatic paucity of interlobular bile ducts: light and electron microscopic evaluation of sequential liver biopsies in early childhood

Liver biopsies and/or autopsy specimens from 17 children (ages 1 week to 5 years) with nonsyndromatic paucity of the interlobular bile ducts were studied by light and electron microscopy. Initial biopsies were obtained before 90 days of age from all patients, and two or more specimens were available from nine. No specific underlying condition was found in nine infants. The remaining cases were associated with Down's syndrome (n = 2), hypopituitarism (n = 2), cystic fibrosis (n = 1), alpha 1-antitrypsin deficiency (n = 1), cytomegalovirus (n = 1) and Ivemark syndrome (n = 1). Before 90 days of age, portal changes included duct paucity and fibrosis. Lobular changes were nonspecific, consisting of cholestasis, giant cell transformation, extramedullary hematopoiesis and perisinusoidal fibrosis. Duct paucity, portal fibrosis and perisinusoidal fibrosis persisted after 90 days. Cholestasis was mild or no longer apparent. Portal changes before 90 days of age appear to be sufficiently distinctive to microscopically distinguish nonsyndromatic from syndromatic paucity. Electron microscopic findings suggest that paucity in nonsyndromatic patients may result from a primary ductal insult: ultrastructural studies revealed bile duct destruction characterized by undulation and breaks in the basal lamina and infiltration of the epithelium by lymphocytes. Bile canalicular dilatation with blunting of microvilli and electron-dense material in the lumen, predominantly seen before 90 days, also reinforces the hypothesis of a primary ductal defect.

A light and electron microscopic study of the regenerative epithelium in the intrahepatic bile duct. Experimental study of local direct instillation of paraquat into the intrahepatic bile ducts of rats

To date, no reliable report on the regeneration of the intrahepatic bile duct epithelium following damage to the duct has been published. In this study, a direct instillation of paraquat dichloride into the intrahepatic bile ducts of rats was carried out, and the livers were examined under light and electron microscopy. One hour after treatment, the biliary epithelia showed degeneration and necrosis, and these changes remained for a considerable period in a large majority of the ducts examined. Three weeks after instillation, low columnar epithelium consisting of hyperchromatic nuclei and eosinophilic cytoplasm was present in a medium-sized bile duct, which was collared by marked periductal fibrosis. Electron microscopically, the eosinophilic epithelium showed a marked increase in the number of rough endoplasmic reticula, ribosomes, mitochondria, and filamentous structures, suggesting an active viability of the cell. Subsequently, the eosinophilic cells were replaced by normal-appearing epithelium, not associated with the periductal fibrosis. The data suggest that an epithelial regeneration occurred in the intrahepatic duct following injury and that this activity may be similar to that of the extrahepatic bile duct epithelium.

Pericanalicular location of hepatocyte lysosomes and effects of fasting: a morphometric analysis

Lysosomes constitute a small proportion of hepatocyte volume, but they play a key degradative role, particularly during catabolic states such as nutritional deprivation. Our preliminary observations in hepatocytes suggested that fasting may alter the distribution of lysosomes, which are thought to congregate about the biliary canaliculus. The current study aimed to provide, in both fed and fasted rats, a quantitative morphometric analysis of lysosomes in the immediate pericanalicular and successively more distant regions. We selected three regions of radius 0 to 2 (region 1), 2 to 4 (region 2) and 4 to 6 micron (region 3) about the bile canaliculus and compared lysosomal numerical and volume densities. In fed rats, numerical and volume densities of both primary and secondary lysosomes were 5 to 10 times greater in region 1 than in region 3. After a 72-hr fast, this gradient was lost due largely to a reduced number of primary and secondary lysosomes in region 1. Our calculations suggest that during fasting, lysosomes are redistributed away from the bile canaliculus towards the more distant cytoplasm rather than being lost from the cell, for example, into bile. The number of overt macroautophagic vacuoles was not altered by fasting. We estimate that, in fed rats, there are approximately 270 lysosomes per hepatocyte, and that 43% of lysosomes are contained in the immediate pericanalicular region 1, which comprises only 7 to 8% of the cytoplasmic volume. The reason for this pericanalicular concentration of lysosomes and the mechanism of the redistribution with fasting remain to be determined.

Early effects of 1,1-dichloroethylene on canalicular and plasma membranes: ultrastructure and stereology

The pathogenesis of 1,1-dichloroethylene (1,1-DCE)-induced hepatotoxicity was investigated in fasted male rats by identifying the earliest morphological alterations in organelles. In situ perfusion-fixed liver tissue was examined by light and electron microscopy at 1, 2, or 3 hr after oral administration of 25, 50, and 100 mg 1,1-DCE/kg in mineral oil. The earliest morphological alterations, which occurred within 1 to 2 hr after 1,1-DCE administration, were dilation of bile canaliculi with an increase in the number of microvilli or membrane fragments in canaliculi and the formation of canalicular diverticuli in centrolobular hepatocytes. Subsequently, microvilli on sinusoidal surfaces were disrupted or lost. Membrane whorls were frequently found in bile canaliculi, the space of Disse, and between the lateral membranes of hepatocytes at early times. As injury progressed, centrolobular hepatocytes retracted from endothelial cells and sinusoidal plasma membranes invaginated to form cytoplasmic vacuoles. Stereological analysis of centrolobular hepatocytes at the 25 mg/kg dose showed a significant increase in canalicular volume density by 3 hr and no detectable alteration in mitochondrial volume density. These results indicate that changes in canalicular shape and microvilli configuration are the earliest morphological alterations following 1-DCE ingestion.

Ultrastructural evidence for the presence of ferritin-iron in the biliary system of patients with iron overload

Ferritin-like particles were observed in bile canaliculi of patients with iron overload. These particles have been further investigated by: a staining method enhancing the size and contrast of ferritin protein, and electron probe microanalysis detecting the presence of the elements iron and phosphorus. Morphological observation of coated vesicles in the cytoplasm adjacent to the bile canaliculi and coated pits in the canalicular membrane suggests a transport mechanism via membrane-bound organelles. Support is given to the theory that part of the iron, stored in the liver, leaves the hepatocyte by excretion of ferritin into the bile.

Primary culture of rat hepatocytes as a model system of canalicular development, biliary secretion, and intrahepatic cholestasis. V. Disturbance of the cellular membrane and bile canalicular ultrastructure induced by chlorpromazine

In the present paper rat hepatocytes in primary monolayer culture were used to investigate the adverse effects of chlorpromazine (CPZ) at the cellular level. As revealed by thin sectioning many of the ultrastructural alterations were comparable to those described for the isolated perfused rat liver under the influence of CPZ. Alterations comprised short-term effects, such as dilation of the rough endoplasmic reticulum and the nuclear envelope, and long-term effects including huge accumulations of myeloid bodies within the cytoplasm as well as dilation and diverticulation of bile canaliculi. Freeze-fracturing revealed the dislocation of intramembrane particles in the sinusoidal plasma membrane which could be detected as early as 30 min after exposure to CPZ. As judged from filipin cytochemistry, alterations in the cholesterol content seems to play a minor role in the process of membrane damage except at the sinusoidal surface where a reduction of cholesterol content may contribute to the impairment of membrane functions. It is concluded that CPZ exerts its cholestatic effect primarily by a rapid disturbance of the membrane architecture of the sinusoidal surface and secondarily by other interactions with the bile secretory apparatus.