Pancreatic enzymes in the epithelium of intrahepatic large bile ducts and in hepatic bile in patients with extrahepatic bile duct obstruction.

AIM--To determine whether pancreatic enzymes are present in hepatic bile and in intrahepatic bile duct epithelium. METHODS--The activity and proteins of pancreatic enzymes (pancreatic alpha-amylase, lipase, trypsin/trypsinogen) in hepatic bile were investigated using biochemical and western blot analyses in 25 patients with extrahepatic bile duct obstruction. Immunolocalization of enzyme proteins was evaluated by immunohistochemistry in 20 necropsy livers with extrahepatic bile duct obstruction. RESULTS--Western blot analysis showed proteins of pancreatic alpha-amylase, lipase, and trypsin in 19 of 25 (76%), 10 of 25 (40%), and 14 of 25 (56%) patients, respectively. Pancreatic alpha-amylase and lipase activities was present in every bile specimen. Radioimmunoassay showed that trypsin was present in every bile sample. Immunohistochemically, the immunoreactivity of the three enzymes was present in epithelia and in the lumina of intrahepatic large bile ducts, septal bile ducts, and peribiliary glands in all cases. CONCLUSIONS--These results strongly suggest that biliary epithelia of larger intrahepatic ducts produce pancreatic alpha-amylase, lipase, and trypsin, and that these enzymes are secreted into the lumina of intrahepatic bile ducts.     

Morphological examination of intrahepatic bile ducts in hepatolithiasis

Summary Numerous glandular elements are characteristically found within and around the intrahepatic bile duct walls in hepatolithiasis. These glandular elements were studied by reconstruction of serial sections and mucus histochemistry. The glands were of two types: glands within the thickened ductal wall (intramural) and those outside the wall (extramural). The former were mucous glands arranged in tubular pattern and the latter seromucous glands arranged in tubuloalveolar pattern. Mucous acini of both glands were rich in neutral, carboxylated and sulfated mucus glycoproteins. Serial section observations showed that the intramural glands communicated with bile duct lumina directly, and the extramural glands with ductal lumina via their own conduits. The intramural glands were usually continuous with the epithelia lining bile ducts, suggesting that they were derived from an invagination and subsequently proliferating epithelium lining bile ducts. The extramural glands may have arisen from a proliferation of the pre-existing peribiliary glands. Hypersecreted mucus from the intramural and extramural glands might be causally related to the development and growth of calculi in the intrahepatic biliary tree.     

Endocrine cells in the intrahepatic biliary tree in normal livers and hepatolithiasis

Endocrine cells in the intrahepatic biliary tree were examined histochemically and immunohistochemically in human infants and adults, as well as in patients with hepatolithiasis. Endocrine cells were sparse but found rather constantly in normal infant livers as well as in adult livers. Almost all endocrine cells were of argyrophil cells or somatostatin-containing cells, and they were usually found in the extramural peribiliary glands in normal livers. On the other hand, in hepatolithiasis in which there were marked proliferation of the peribiliary glands and hyperplasia of surface-lining epithelia, many kinds of endocrine cells were seen in the extramural and intramural peribiliary glands, as well as in the lining epithelial layer. Furthermore, these endocrine cells were hyperplastic in the affected intrahepatic bile duct in two patients with hepatolithiasis. These data suggested that argyrophil cells and somatostatin-containing cells are physiologically present in the intrahepatic biliary tree, and many kinds of other endocrine cells newly appear and even proliferate in hepatolithiasis. These findings imply the participation of reported action of these hormones on bile flow in normal livers and hepatolithiasis.     

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.     

Pathologic observations of intrahepatic peribiliary glands in 1,000 consecutive autopsy livers: IV. Hyperplasia of intramural and extramural glands.

Hyperplastic changes of intrahepatic peribiliary glands have rarely been reported, with the exception of hepatolithiasis. To determine whether there are any hyperplastic changes in the glands in livers without hepatolithiasis, we examined 1,000 consecutive autopsy liver specimens that had no hepatolithiasis. The glands were divided into intramural mucous glands and extramural seromucous glands. The hyperplastic changes were found in "normal" livers and in livers with various hepatobiliary diseases, and they were classified into three categories: hyperplasia of intramural glands (49 cases; 4.9%), hyperplasia of extramural serous acini (35 cases; 3.5%), and hyperplasia of extramural mucous acini (92 cases; 9.2%). Two or more of these three hyperplastic changes occasionally coexisted in the same liver. Hyperplasia of intramural glands was seen rather evenly in normal livers and in livers with various hepatobiliary diseases. Prevalence of hyperplasia of extramural serous acini was high in intrahepatic cholangitis and submassive hepatic necrosis. Prevalence of hyperplasia of extramural mucous acini was high in cirrhosis, submassive hepatic necrosis, cholangitis, systemic infection, and extrahepatic biliary obstruction. The hyperplastic intramural glands and mucous acini of extramural glands contained more neutral, carboxylated, and sulfated mucin than normal glands. Although their pathogenesis is unclear, these hyperplastic changes may enhance seromucous secretion into biliary lumens and may lead to biliary dysfunctions such as retardation of bile flow and increased bile viscosity. These hyperplastic changes may be preexisting conditions predisposing to hepatolithiasis.     

Aberrant expression of stem cell factor on biliary epithelial cells and peribiliary infiltration of c-kit-expressing mast cells in hepatolithiasis and primary sclerosing cholangitis: a possible contribution to bile duct fibrosis

Hepatolithiasis and primary sclerosing cholangitis (PSC) are intractable chronic biliary diseases. In hepatolithiasis, bilirubin-calcium stones are packed in multiple irregularly dilated intrahepatic bile ducts. In PSC, small bilirubin-calcium stones develop terminally. The progressive periductal fibrosis with dilated and stenotic bile ducts in these two diseases may play a role in their incurability. This immunohistochemical study has investigated the expression of some factors that might be involved in fibrogenesis in hepatolithiasis and PSC. Many mast cells positive for c-kit were found in the periductal and ductal fibrosis around the intrahepatic large bile ducts and also around the proliferative peribiliary glands. These mast cells also expressed basic fibroblast growth factor and/or tumour necrosis factor-alpha, which are known as fibrogenetic factors. It was of interest that the aberrant expression of stem cell factor (SCF), a ligand of c-kit, was demonstrated on biliary epithelia of the dilated and stenotic bile ducts showing periductal fibrosis and inflammation and also of the proliferated peribiliary glands in hepatolithiasis and PSC, while no such expression was seen in non-affected bile ducts in hepatolithiasis or in the bile ducts in normal livers. Some of the infiltrating mononuclear cells around the SCF-expressing bile ducts were also positive for SCF. It seems likely that aberrantly expressed SCF on biliary epithelial cells accumulates and stimulates mast cells via the c-kit receptor and that these up-regulated mast cells induce progressive periductal and portal fibrosis by displaying fibrogenetic factors in hepatolithiasis and PSC.     

Monolobar ductal plate malformation disease of the liver

We herein report a unique monolobar hepatic disease composed of Caroli's disease, peribiliary cysts, ductal plate malformations, peribiliary gland proliferation, hepatolithiasis, and portal phlebosclerosis with thrombi. A 73‐year‐old man underwent abdominal imaging, which revealed multiple segmental dilations of the left intrahepatic bile ducts. Polycystic kidney diseases were absent. Intrahepatic cholangiocarcinoma was suspected, and extended left lobectomy of the liver was preformed. Grossly, the hepatic left lobe was atrophic, and partly replaced by fibrous tissue. The intrahepatic bile ducts were dilated (Caroli's disease), and showed small calcium bilirubinate hepatoliths. Microscopically, the intrahepatic bile duct showed non‐obstructive segmental dilations (Caroli's disease), numerous peribiliary cysts, numerous ductal plate malformations, proliferation of intrahepatic peribiliary glands, and calcium bilirubinate hepatolithiasis. Portal veins showed phlebosclerosis with thrombi. Immunohistochemically, the various biliary epithelial cells were positive for cytokeratin (CK) 7, 8, 18, and 19, and for MUC6 and CD10. They were negative for MUC2 and MUC5AC. The ductal plate malformations were positive for fetal biliary antigen MUC1, but other biliary cell types were negative for MUC1. The present case resembles ‘monolobar Caroli's disease’. We believe that the present monolobular liver disease was congenital in origin.     

Marked diffuse dilations of the biliary tree associated with intrahepatic calculi,biliary sludges and a mucinous cyst of the pancreatic head in a 99-year-old woman

A 99-year-old woman was admitted to Shizuoka Shimizu Municipal Hospital because of fever and anasarca. Imaging and laboratory tests showed pneumonia, urinary tract infection, and cardiac failure. The patient died 20 days after admission. An autopsy revealed marked diffuse dilations of the biliary tree ranging from the lower common bile duct to intrahepatic bile ducts. Intrahepatic calcium bilirubinate stones and biliary sludges were recognized within the dilated bile ducts. A unilocular cyst (2 cm in diameter) was present in the pancreatic head adjacent to the lower common bile duct, and it appeared to compress the common bile duct. Histologically, the walls of the dilated biliary tree showed proliferation of peribiliary glands, fibrosis, and infiltration of lymphocytes and neutrophils (cholangitis). The lumens of the dilated biliary ducts contained neutral and acidic mucins, fibrinous materials, bacteria, neutrophils, and Aspergillus fungi, in addition to the calculi and sludges. The background liver showed atrophy (400 g). The pancreatic unilocular cyst was composed of mucous columnar cells with a few infoldings, and the pancreas also showed foci of mucinous duct hyperplasia and ectasia; the pathological diagnosis of the cyst was cystic dilations of a pancreatic duct branch (mucinous ductal ectasia or mucinous cyst). Other lesions included aspiration pneumonia, emaciation, atrophy of systemic organs, gastric leiomyoma, serous cystadenoma of the right ovary, and arteriosclerotic nephrosclerosis. The present case suggests that a mucinous cyst of the pancreas may compress the biliary tree and lead to marked diffuse dilations of the biliary tree. Alternatively, the dilations of the bile ducts may be associated with aging or may be of congenital origin. The dilated bile ducts may, in turn, give rise to bacterial and fungal cholangitis and formation of biliary sludges and intrahepatic calcium bilirubinate stones.     

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.     

Characterization of biliary intra-epithelial lymphocytes at different anatomical levels of intrahepatic bile ducts under normal and pathological conditions: numbers of CD4+CD28- intra-epithelial lymphocytes are increased in primary biliary cirrhosis

Distribution of intra-epithelial lymphocytes along intrahepatic biliary tree (bIEL), and their density and phenotype were examined in normal and diseased livers, particularly in primary biliary cirrhosis (PBC). Immunohistochemically, bIEL were examined in 28 normal livers, 13 cases of chronic viral hepatitis (CVH), 13 cases of PBC, five cases of primary sclerosing cholangitis (PSC), seven cases of extrahepatic biliary obstruction (EBO), and 16 hepatolithiatic livers. In normal livers, bIEL were relatively dense at large and septal bile ducts compared to interlobular ducts. Most of them were positive for CD3 and CD8, while a few were positive for CD4, CD20 and CD57. In CVH, PSC and EBO, neither distribution, phenotype nor density of bIEL differed from normal liver. In hepatolithiasis, numbers of CD8(+)bIEL were increased in stone-containing ducts. In PBC, numbers of CD4(+)CD28(-)bIEL, which are reportedly responsible for target tissue destruction in autoimmune diseases, were markedly increased in damaged interlobular ducts. In conclusion, CD3(+)CD8(+)bIEL may be involved in immune homeostasis of intrahepatic bile ducts in normal livers and in CVH, PSC and EBO. Altered distribution and phenotypes of bIEL in PBC and hepatolithiasis may reflect their participation in biliary lesions. Increased CD4(+)CD28(-)bIEL in damaged bile ducts of PBC may be related to immune-mediated biliary damage.     

Cholesterol hepatolithiasis with peribiliary cysts

A 78-year-old man was admitted to our clinic because of fatigue. Imaging modalities showed beaded stricture and dilation of the intrahepatic left segmental bile duct. Anomalous pancreatico-biliary ductal union and polycystic kidney disease were absent. Resection of the hepatic left lobe was performed. Grossly, cholesterol stones were impacted in the dilated intrahepatic large bile ducts, and multiple tiny cysts measuring 2-8 mm were noted in the peribiliary areas (peribiliary cysts). Histologically, the cholesterol hepatoliths consisted of cholesterol empty spaces and fibrinous materials, and, in places, foreign body giant cells were seen around the cholesterol crystals. The peribiliary cysts were lined by a layer of cuboidal epithelia. They were intimately intermingled with intrahepatic peribiliary glands, and a close association between the two components was recognized in some places. A mild degree of ascending cholangitis was noted. Bile duct anomalies including von-Meyenburg complexes and simple cysts were not recognized. Peribiliary cysts have been reported in various liver diseases, including portal hypertension, portal thrombosis, cirrhosis, hepatocellular carcinoma, and adult polycystic kidney disease. However, to the best of our knowledge, there have been no reports on peribiliary cysts developing in hepatolithiasis. The present case indicates that peribiliary cysts occur in cholesterol hepatolithiasis, and suggests that they are derived from cystic dilations of intrahepatic peribiliary glands.     

Histological features and interphase nucleolar organizer regions in hyperplastic, dysplastic and neoplastic epithelium of intrahepatic bile ducts in hepatolithiasis

Neoplastic transformation occurs in the intrahepatic biliary tree in hepatolithiasis. The present study aimed to clarify the neoplastic processes by correlating the histological features of the bile duct lesions with counts of interphase argyrophilic nucleolar organizer regions (AgNORs), which reflect cell proliferative activity. We studied 55 cases of hepatolithiasis and 25 normal autopsy livers. The biliary epithelial lesions in hepatolithiasis were divisible into hyperplasia, dysplasia and neoplasia. These lesions were found in bile ducts containing calculi. All cases of hepatolithiasis showed a varied degree of hyperplasia. Additionally, eight cases showed dysplasia, five non-invasive intraductal adenocarcinoma and 10 invasive adenocarcinoma. Cases of non-invasive and invasive carcinoma frequently harboured areas of dysplasia, and areas of dysplasia and non-invasive carcinoma, respectively. The mean and standard deviation of the number of interphase AgNORs in the normal and abnormal biliary epithelium showed a step-wise increase in the following order: normal (1.32 +/- 0.36), hyperplasia (1.52 +/- 0.37), dysplasia (2.28 +/- 0.56), non-invasive carcinoma (3.23 +/- 1.00), and invasive carcinoma (3.72 +/- 0.77). These histological and cell kinetic observations suggest that, in hepatolithiasis, carcinogenesis in bile duct epithelial cells progresses in a multi-step manner, through hyperplasia, dysplasia, non-invasive adenocarcinoma and invasive adenocarcinoma.     

Pathologic features of hepatolithiasis in Japan

A national survey of pathologic features of hepatolithiasis was conducted in Japan. The significance of hepatobiliary lesions in the pathogenesis of hepatolithiasis was evaluated in 31 autopsy livers and 242 surgically resected livers. Eighty-two percent shared several morphologic and clinical features, eg, the presence of multiple calcium bilirubinate or brown pigment stones within the intrahepatic duct and a characteristic hepatobiliary morphology. These cases were distributed throughout Japan without distinct geographic differences. The stones were found in the left and/or right hepatic duct and/or their tributaries. The ducts that contained stones had uneven dilatation of their lumena with focal stenosis. The walls of the involved ducts were thickened mainly by fibrosis. The hepatic parenchyma associated with stones within intrahepatic bile ducts showed mild to severe atrophy and fibrosis. Histologically, the ducts that contained stones showed fibrosis, proliferation of mucous and serous glands, and inflammatory cell infiltration in their walls and the periductal tissue. A large amount of mucus secreted from the affected ducts was seen within the biliary sludge and calcium bilirubinate stones were found in the involved ductal lumena. These findings suggest that the large amount of mucus and the formation of unevenly dilated ductal lumena may be important in the formation of intrahepatic calculi because these factors may favor nucleation and promote local bile stasis, thereby accentuating the ductal changes and stone formation (a vicious cycle).     

Primary hepatolithiasis, recurrent pyogenic cholangitis, and oriental cholangiohepatitis: a tale of 3 countries

Primary hepatolithiasis (HL), recurrent pyogenic cholangitis, and oriental cholangiohepatitis are terms commonly used in Japan, Hong Kong, and Korea respectively, and describing the different aspects of the same disease, with "HL" indicating the pathologic changes, "recurrent pyogenic cholangitis" emphasizing the clinical presentation and suppurative inflammation, and "oriental cholangiohepatitis" highlighting its ethnic preference and mysterious nature. HL is predominantly a disease of the far east and shows great regional differences in the incidence and the type of intrahepatic stones. Pathologically, it is characterized by pigmented calcium bilirubinate stones within dilated intrahepatic bile ducts featuring chronic inflammation, mural fibrosis, and proliferation of peribiliary glands, without extrahepatic biliary obstruction. Episodes of suppurative inflammation cumulate in sclerosing cholangitis in peripheral ducts and parenchymal fibrosis from scarring and collapse. Mass-forming inflammatory pseudotumor and neoplasms-like intraductal papillary neoplasms and cholangiocarcinoma are increasingly recognized complications. Bacterial infection and dietary factors are believed to be important in the formation of pigment stones within intrahepatic bile ducts, whereas parasitic infestation is likely coincidental. With improvement of environmental conditions and westernization of diet, the incidence of pigment stones has decreased. At the same time, cholesterol stones with milder clinical manifestations and pathologic changes are increasingly recognized, and for which stone dissolution therapy can be considered. Understanding the underlying pathology avoids confusion with other diseases more prevalent in the western world, and allows correct selection of the appropriate treatment.     

Histopathological distinction and evaluation of biliary and peribiliary cysts in pig liver

The majority of hepatic cysts identified in animals are considered to derive from the intrahepatic bile ducts (biliary cysts). An alternative origin is the peribiliary glands located in the hilum of the liver and large portal tracts (peribiliary cysts). The distinction between biliary and peribiliary cysts, and whether these have different clinical significance, has rarely been considered previously. This study reports the pathological features of five cystic porcine livers. Four of these five livers had both biliary and peribiliary cysts and the fifth had only biliary cysts. Biliary cysts were not associated with distortion of adjacent hepatic parenchyma, whereas peribiliary cysts appeared to cause local compression and circulatory disturbance. It would therefore appear that peribiliary cysts have greater potential clinical significance than those of biliary origin.     

Distortion in TGFβ1 peptide immunolocalization in biliary atresia: Comparison with the normal pattern in the developing human intrahepatic bile duct system

Biliary atresia is an important cause of neonatal obstructive jaundice in which there is inflammation, sclerosis and eventual obliteration of the bile duct system. Its onset may be antenatal, affecting the normal development of the biliary system. The intrahepatic biliary system is derived from the ductal plate, a sheath of cuboidal epithelium that appears at the hepatocyte-mesenchymal junction around the portal vein branches at 6 weeks gestation. This epithelial structure is moulded into a network of tubular bile ducts by the proliferating mesenchyme. Certain portions of the ductal plate are selected to become definitive bile ducts, while redundant biliary epithelium is deleted. The molecular dynamics controlling the intra-uterine development of the biliary system in humans are not yet clearly understood. Transforming growth factor-β1 is a cytokine that stimulates mes-enchymal proliferation and inhibits epithelial growth, and has been shown to be important in organogenesis. In the present study, the pattern of TGFβ1 peptide immunolocalization was investigated with the aid of computerized image analysis, in normal human bile duct development and in biliary atresia. TGFβ1 peptide was detected within hepata-cytes and ductal plate epithelium from 7 weeks gestation; increased TGFβ1 immunoreactivity was present within the epithelium of developing bile ducts at 13 weeks gestation, and apical polarization of the cytokine was observed from 16 weeks gestation. In biliary atresia, the TGFβ1 immunoreactivity pattern within the bile duct structures at the porta hepatis and within intrahepatic portal tracts resembled that of the primitive ductal plate, and there was no significant apical polarization. This may indicate a developmental arrest in the normal ductal plate remodelling process in biliary atresia, and suggests an underlying epithelial-mesenchymal interactive disorder.     

Expression of matrix proteinases during human intrahepatic bile duct development. A possible role in biliary cell migration.

Primitive biliary cells are known to migrate from the ductal plate into the mesenchyme during human intrahepatic bile duct development, and this migration process is essential for normal development of intrahepatic bile ducts. However, its molecular mechanism is unknown. Matrix proteinases play an important role in cell migration during cancer invasion and organ development. In this study, we therefore investigated in situ expression of matrix metalloproteinases (MMP) and tissue inhibitors of MMP (TIMP) during human intrahepatic bile duct development, using 32 human fetal livers. We also examined in situ expression of trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B, which are matrix proteinases and activators of MMP. MMP-1 expression was noted in the ductal plate and migrating primitive biliary cells. MMP-2, MMP-3, and MMP-9 were expressed in the ductal plate. TIMP-1 and TIMP-2 were expressed in the ductal plate and migrating primitive biliary cells. Trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B were also expressed in primitive biliary cells. These data suggest that MMP, trypsinogen/trypsin, chymotrypsinogen/chymotrypsin, and cathepsin B play a critical role in biliary cell migration during human intrahepatic bile duct development by degrading extracellular matrix proteins. The data also suggest that MMP inhibitors (TIMP-1 and TIMP-2) and MMP activators (trypsin, chymotrypsin, and cathepsin B) play an important role in biliary cell migration. The coordinated expression of MMP, MMP inhibitors, and MMP activators may be necessary for the normal development of human intrahepatic bile ducts.     

Convoluted bile ducts in the liver of the larval lamprey, Petromyzon marinus L

Summary The three-dimensional structure of the bile ducts and their relationship to the blood vessels were studied in the larval lamprey by scanning electron microscopy of the intact tissue and of biliary and vascular casts. The intrahepatic gall bladder is situated in the cephalic portion of the liver and a cystic duct is connected to a straight intrahepatic common bile duct, which extends to the extrahepatic bile duct at the caudal end of the liver. Several smaller intrahepatic common bile ducts are connected directly to the intrahepatic common bile duct, are convoluted or serpiginous and are surrounded intimately by sinusoids. This arrangement enables the bile ducts to have increased surface area exposed to blood vessels. The functional significance of this arrangement is discussed with respect to the modification of bile through the transport of solutes and the similarity of this bilio-vascular relationship to the peribiliary vascular plexus of the mammalian liver.     

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.