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Ruggero Oddi was a talented scientist who initiated the modern era of biliary system physiology, not only with the anatomical discovery of the hepatopancreatic sphincter, but also with the detailed description of its spinal center and nerve regulation. However, his personal and scientific life were determined by an incredible series of unfortunate circumstances. Until now most of these events have been unknown, while the few known have produced biographies distorted by fake interpretations. The purpose of this article is to document Oddi's biography and scientific production in detail, comprehensively framing the scientific environment in which his discoveries occurred. It clears many misinterpretations about events in Oddi's life and academic career, bringing to a new light his figure as scientist in gastroenterological field., Competing Interests: Declaration of conflicting interestsThe author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article.

During biliary tree homeostasis, BECs are largely in a quiescent state and their turnover is slow for maintaining normal tissue homeostasis. BTSCs continually replenish new BECs in the luminal surface of EHBDs. In response to various types of biliary injuries, distinct cellular sources, including HPCs, BTSCs, hepatocytes, and BECs, repair or regenerate the injured bile duct. BEC, biliary epithelial cell; BTSC, biliary tree stem/progenitor cell; EHBD, extrahepatic bile ducts; HPC, hepatic progenitor cell.The biliary tree comprises intrahepatic bile ducts and extrahepatic bile ducts lined with epithelial cells known as biliary epithelial cells (BECs). BECs are a common target of various cholangiopathies for which there is an unmet therapeutic need in clinical hepatology. The repair and regeneration of biliary tissue may potentially restore the normal architecture and function of the biliary tree. Hence, the repair and regeneration process in detail, including the replication of existing BECs, expansion and differentiation of the hepatic progenitor cells and biliary tree stem/progenitor cells, and transdifferentiation of the hepatocytes, should be understood. In this paper, we review biliary tree homeostasis, repair, and regeneration and discuss the feasibility of regenerative therapy strategies for cholangiopathy treatment., Competing Interests: None declared., (Thieme. All rights reserved.)

Yes-associated protein 1 (YAP1) regulates cell plasticity during liver injury, regeneration, and cancer, but its role in liver development is unknown. We detect YAP1 activity in biliary cells and in cells at the hepatobiliary bifurcation in single-cell RNA sequencing analysis of developing livers. Deletion of Yap1 in hepatoblasts does not impair Notch-driven SOX9+ ductal plate formation but does prevent the formation of the abutting second layer of SOX9+ ductal cells, blocking the formation of a patent intrahepatic biliary tree. Intriguingly, these mice survive for 8 months with severe cholestatic injury and without hepatocyte-to-biliary transdifferentiation. Ductular reaction in the perihilar region suggests extrahepatic biliary proliferation, likely seeking the missing intrahepatic biliary network. Long-term survival of these mice occurs through hepatocyte adaptation via reduced metabolic and synthetic function, including altered bile acid metabolism and transport. Overall, we show YAP1 as a key regulator of bile duct development while highlighting a profound adaptive capability of hepatocytes., Competing Interests: Declaration of interests The authors declare no competing interests., (Copyright © 2021 The Author(s). Published by Elsevier Inc. All rights reserved.)

Bile formation is a fundamental physiological process that is vital to the survival of all vertebrates. However, little was known about the mechanisms of this secretion until after World War II. Initial studies involved classic physiologic studies in animal models and humans, which progressed to include studies in isolated cells and membrane vesicles. The advent of molecular biology then led to the identification of specific transport systems that are the determinants of this secretion. Progress in this field was reviewed in the American Physiologic Society's series on "Comprehensive Physiology" in 2013. Herein, we provide an in-depth update of progress since that time., Competing Interests: Conflict of interest The authors declare no conflicts of interest that pertain to this work. Please refer to the accompanying ICMJE disclosure forms for further details., (Copyright © 2021. Published by Elsevier B.V.)

The biliary system is routinely accessed for clinical purposes via endoscopic retrograde cholangiopancreatography (ERCP). We previously pioneered ERCP-mediated hydrodynamic injection in large animal models as an innovative gene delivery approach for monogenic liver diseases. However, the procedure poses potential safety concerns related mainly to liver or biliary tree injury. Here, we sought to further define biliary hydrodynamic injection parameters that are well-tolerated in a human-sized animal model. ERCP was performed in pigs, and hydrodynamic injection carried out using a novel protocol to reduce duct wall stress. Each pig was subjected to multiple repeated injections to expedite testing and judge tolerability. Different injection parameters (volume, flow rate) and injection port diameters were tested. Vital signs were monitored throughout the procedure, and liver enzyme panels were collected pre- and post-procedure. Pigs tolerated repeated biliary hydrodynamic injections with only occasional, mild, isolated elevation in aspartate aminotransferase (AST), which returned to normal levels within one day post-injection. All other liver tests remained unchanged. No upper limit of volume tolerance was reached, which suggests the biliary tree can readily transmit fluid into the vascular space. Flow rates up to 10 mL/sec were also tolerated with minimal disturbance to vital signs and no anatomic rupture of bile ducts. Measured intrabiliary pressure was up to 150 mmHg, and fluid-filled vesicles were induced in liver histology at high flow rates, mimicking the changes in histology observed in mouse liver after hydrodynamic tail vein injection. Overall, our investigations in a human-sized pig liver using standard clinical equipment suggest that ERCP-guided hydrodynamic injection will be safely tolerated in patients. Future investigations will interrogate if higher flow rates and pressure mediate higher DNA delivery efficiencies., Competing Interests: Conflict of Interest: R.L.K, Y.H., V.K., and F.M.S. have a patent application filed on the work. All other authors do not have conflict of interests. There are no other licensing or consulting interests; this does not alter our adherence to PLOS ONE policies on sharing data and materials.

Background: Preconditioning of donor livers before organ retrieval may improve organ quality after transplantation. We investigated whether preconditioning with metformin reduces preservation injury and improves hepatobiliary function in rat donor livers during ex situ normothermic machine perfusion (NMP) and after orthotopic liver transplantation., Methods: Lewis rats were administered metformin via oral gavage, after which a donor hepatectomy was performed followed by a standardized cold storage period of 4 hours. Graft assessment was performed using NMP via double perfusion of the hepatic artery and portal vein. In an additional experiment, rat donor livers preconditioned with metformin were stored on ice for 4 hours and transplanted to confirm postoperative liver function and survival. Data were analyzed and compared with sham-fed controls., Results: Graft assessment using NMP confirmed that preconditioning significantly improved ATP production, markers for hepatobiliary function (total bile production, biliary bilirubin, and bicarbonate), and significantly lowered levels of lactate, glucose, and apoptosis. After orthotopic liver transplantation, metformin preconditioning significantly reduced transaminase levels., Conclusions: Preconditioning with metformin lowers hepatobiliary injury and improves hepatobiliary function in an in situ and ex situ model of rat donor liver transplantation.

The autonomic nervous system plays a role in a variety of liver regenerative and metabolic functions, including modulating bile secretion and cholangiocyte and hepatobiliary progenitors of the canals of Hering. However, the nature and location of nerves which link to the proximal biliary tree have remained uncertain. We investigate the anatomic relationship of nerves to the proximal biliary tree including the putative stem/progenitor cell niche of the canal of Hering. Using double immunostaining (fluorescence, histochemistry) to highlight markers of cholangiocytes (biliary-type keratins), nerves (S100, neurofilament protein, PGP9.5, tyrosine hydroxylase), and stellate cells (CRBP-1), we examined sections from normal adult livers from autopsy or surgical resections. There is extensive contact between nerves and interlobular bile ducts, bile ductules, and canals of Hering (CoH). In multiple serial sections from 4 normal livers, biliary-nerve contacts were seen in all of these structures and were more common in the interlobular bile ducts (78/137; 57%) than in the ductules and CoH (95/294; 33%) (p < 0.001). Contacts appear to consist of nerves in juxtaposition to the biliary basement membrane, though crossing through basement membrane to interface directly with cholangiocytes is also present. These nerves are positive for tyrosine hydroxylase and are, thus, predominately adrenergic. Electron microscopy confirms nerves closely approximating ductules. Nerve fiber-hepatic stellate cell juxtaposition is observed but without stellate cell approximation to cholangiocytes. We present novel findings of biliary innervation, perhaps mediated in part, by direct cholangiocyte-nerve interactions. The implications of these findings are protean for studies of neuromodulation of biliary physiology and hepatic stem/progenitor cells.

Background: Chronic liver diseases are frequently accompanied with activation of biliary epithelial cells (BECs) that can differentiate into hepatocytes and cholangiocytes, providing an endogenous back-up system. Functional studies on BECs often rely on isolations of an BEC cell population from healthy and/or injured livers. However, a consensus on the characterization of these cells has not yet been reached. The aim of this study was to compare the publicly available transcriptome profiles of human and mouse BECs and to establish gene signatures that can identify quiescent and activated human and mouse BECs., Methods: We used publicly available transcriptome data sets of human and mouse BECs, compared their profiles and analyzed co-expressed genes and pathways. By merging both human and mouse BEC-enriched genes, we obtained a quiescent and activation gene signature and tested them on BEC-like cells and different liver diseases using gene set enrichment analysis. In addition, we identified several genes from both gene signatures to identify BECs in a scRNA sequencing data set., Results: Comparison of mouse BEC transcriptome data sets showed that the isolation method and array platform strongly influences their general profile, still most populations are highly enriched in most genes currently associated with BECs. Pathway analysis on human and mouse BECs revealed the KRAS signaling as a new potential pathway in BEC activation. We established a quiescent and activated BEC gene signature that can be used to identify BEC-like cells and detect BEC enrichment in alcoholic hepatitis, non-alcoholic steatohepatitis (NASH) and peribiliary sclerotic livers. Finally, we identified a gene set that can distinguish BECs from other liver cells in mouse and human scRNAseq data., Conclusions: Through a meta-analysis of human and mouse BEC gene profiles we identified new potential pathways in BEC activation and created unique gene signatures for quiescent and activated BECs. These signatures and pathways will help in the further characterization of this progenitor cell type in mouse and human liver development and disease., Competing Interests: The authors declare no conflict of interest.

Introduction: This audit investigated hepatobiliary function imaging in UK hospitals, reviewing protocol differences in acquisition and processing parameters and the effect on calculated gallbladder ejection fraction (GBEF)., Participants and Methods: Two dynamic data sets were available: one continuous dynamic data set, and the other with a 5-min break to administer the fatty stimulus. Participants used a set of 12 anonymized patient data sets most similar to their standard protocol calculating GBEF using their routine method., Results: Fifty-two UK centres responded. Across all centres for all data sets, there was large variability in GBEF quoted, mostly owing to variations in the calculation method, motion correction and imaging type/times. The largest contributor to GBEF variation was time acquired after stimulus which varied from 20 to 70 min. Only 48.1% centres acquired for 60 min after stimulus, which is the acquisition time stated in normal range references. Overall, 13.5% participating centres administered fatty stimuli that fell below the recommended 10 g. Widespread variations were found in GBEF normal ranges and fatty stimulus administration. Motion correction has a large effect on GBEF; in one data set, motion correction alone changed GBEF from 44 to 9%, but 25% of the participants stated motion correction was not used., Conclusion: The authors proposed gold standard is fat content of the stimulus should be at least 10 g; and images should be acquired for 60 min after stimulus. If GBEF is quoted, motion correction should be used, and if compared with a normal range, the stimulus used must fit with the reference.

Two distinct stem/progenitor cell populations of biliary origin have been identified in the adult liver and biliary tree. Hepatic Stem/progenitor Cells (HpSCs) are bipotent progenitor cells located within the canals of Hering and can be differentiated into mature hepatocytes and cholangiocytes; Biliary Tree Stem/progenitor Cells (BTSCs) are multipotent stem cells located within the peribiliary glands of large intrahepatic and extrahepatic bile ducts and able to differentiate into hepatic and pancreatic lineages. HpSCs and BTSCs are endowed in a specialized niche constituted by supporting cells and extracellular matrix compounds. The actual contribution of these stem cell niches to liver and biliary tree homeostatic regeneration is marginal; this is due to the high replicative capabilities and plasticity of mature parenchymal cells (i.e., hepatocytes and cholangiocytes). However, the study of human liver and biliary diseases disclosed how these stem cell niches are involved in the regenerative response after extensive and/or chronic injuries, with the activation of specific signaling pathways. The present review summarizes the contribution of stem/progenitor cell niches in human liver diseases, underlining mechanisms of activation and clinical implications, including fibrogenesis and disease progression., Competing Interests: The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.

Background: Physical inactivity puts the populations at risk of several health problems, while regular physical activity brings beneficial effects on cardiovascular disease, mortality and other health outcomes, including obesity, glycaemic control and insulin resistance. The hepatobiliary tract is greatly involved in several metabolic aspects which include digestion and absorption of nutrients in concert with intestinal motility, bile acid secretion and flow across the enterohepatic circulation and intestinal microbiota. Several metabolic abnormalities, including nonalcoholic fatty liver as well as cholesterol cholelithiasis, represent two conditions explained by changes of the aforementioned pathways., Materials and Methods: This review defines different training modalities and discusses the effects of physical activity in two metabolic disorders, that is nonalcoholic fatty liver disease (NAFLD) and cholelithiasis. Emphasis is given to pathogenic mechanisms involving intestinal bile acids, microbiota and inflammatory status., Results: A full definition of physical activity includes the knowledge of aerobic and endurance exercise, metabolic equivalent tasks, duration, frequency and intensity, beneficial and harmful effects. Physical activity influences the hepatobiliary-gut axis at different levels and brings benefits to fat distribution, liver fat and gallbladder disease while interacting with bile acids as signalling molecules, intestinal microbiota and inflammatory changes in the body., Conclusions: Several beneficial effects of physical activity are anticipated on metabolic disorders linking liver steatosis, gallstone disease, gut motility, enterohepatic circulation of signalling bile acids in relation to intestinal microbiota and inflammatory changes., (© 2018 Stichting European Society for Clinical Investigation Journal Foundation.)

Aim: To elucidate the role of STAT3 in hepatocarcinogenesis and biliary ductular proliferation following chronic liver injury., Methods: We investigated thioacetamide (TAA)-induced liver injury, compensatory hepatocyte proliferation, and hepatocellular carcinoma (HCC) development in hepatic STAT3-deficient mice. In addition, we evaluated TAA-induced biliary ductular proliferation and analyzed the activation of sex determining region Y-box9 (SOX9) and Yes-associated protein (YAP), which regulate the transdifferentiation of hepatocytes to cholangiocytes., Results: Both compensatory hepatocyte proliferation and HCC formation were significantly decreased in hepatic STAT3-deficient mice as compared with control mice. STAT3 deficiency resulted in augmentation of hepatic necrosis and fibrosis. On the other hand, biliary ductular proliferation increased in hepatic STAT3-deficient livers as compared with control livers. SOX9 and YAP were upregulated in hepatic STAT3-deficient hepatocytes., Conclusion: STAT3 may regulate hepatocyte proliferation as well as transdifferentiation into cholangiocytes and serve as a therapeutic target for HCC inhibition and biliary regeneration., Competing Interests: Conflict-of-interest statement: The authors have no conflicts of interest.

The treatment of common bile duct (CBD) disorders, such as biliary atresia or ischemic strictures, is restricted by the lack of biliary tissue from healthy donors suitable for surgical reconstruction. Here we report a new method for the isolation and propagation of human cholangiocytes from the extrahepatic biliary tree in the form of extrahepatic cholangiocyte organoids (ECOs) for regenerative medicine applications. The resulting ECOs closely resemble primary cholangiocytes in terms of their transcriptomic profile and functional properties. We explore the regenerative potential of these organoids in vivo and demonstrate that ECOs self-organize into bile duct-like tubes expressing biliary markers following transplantation under the kidney capsule of immunocompromised mice. In addition, when seeded on biodegradable scaffolds, ECOs form tissue-like structures retaining biliary characteristics. The resulting bioengineered tissue can reconstruct the gallbladder wall and repair the biliary epithelium following transplantation into a mouse model of injury. Furthermore, bioengineered artificial ducts can replace the native CBD, with no evidence of cholestasis or occlusion of the lumen. In conclusion, ECOs can successfully reconstruct the biliary tree, providing proof of principle for organ regeneration using human primary cholangiocytes expanded in vitro.

The complex architecture of the liver biliary network represents a structural prerequisite for the formation and secretion of bile as well as excretion of toxic substances through bile ducts. Disorders of the biliary tract affect a significant portion of the worldwide population, often leading to cholestatic liver diseases. Cholestatic liver disease is a condition that results from an impairment of bile formation or bile flow to the gallbladder and duodenum. Cholestasis leads to dramatic changes in biliary tree architecture, worsening liver disease and systemic illness. Recent studies show that the prevalence of cholestatic liver diseases is increasing. The availability of well characterized animal models, as well as development of visualization approaches constitutes a critical asset to develop novel pathogenetic concepts and new treatment strategies.

Bile, the central metabolic product of the liver, is transported by the bile canaliculi network. The impairment of bile flow in cholestatic liver diseases has urged a demand for insights into its regulation. Here, we developed a predictive 3D multi-scale model that simulates fluid dynamic properties successively from the subcellular to the tissue level. The model integrates the structure of the bile canalicular network in the mouse liver lobule, as determined by high-resolution confocal and serial block-face scanning electron microscopy, with measurements of bile transport by intravital microscopy. The combined experiment-theory approach revealed spatial heterogeneities of biliary geometry and hepatocyte transport activity. Based on this, our model predicts gradients of bile velocity and pressure in the liver lobule. Validation of the model predictions by pharmacological inhibition of Rho kinase demonstrated a requirement of canaliculi contractility for bile flow in vivo. Our model can be applied to functionally characterize liver diseases and quantitatively estimate biliary transport upon drug-induced liver injury., (Copyright © 2017 The Author(s). Published by Elsevier Inc. All rights reserved.)

Despite decades of basic research, biliary diseases remain prevalent, highly morbid, and notoriously difficult to treat. We have, however, dramatically increased our understanding of biliary developmental biology, cholangiocyte pathophysiology, and the endogenous mechanisms of biliary regeneration and repair. All of this complex and rapidly evolving knowledge coincides with an explosion of new technological advances in the area of regenerative medicine. New breakthroughs such as induced pluripotent stem cells and organoid culture are increasingly being applied to the biliary system; it is only a matter of time until new regenerative therapeutics for the cholangiopathies are unveiled. In this review, the authors integrate what is known about biliary development, regeneration, and repair, and link these conceptual advances to the technological breakthroughs that are collectively driving the emergence of a new global field in biliary regenerative medicine., (Thieme Medical Publishers 333 Seventh Avenue, New York, NY 10001, USA.)

Unlabelled: Many regulatory pathways are involved in liver regeneration after partial hepatectomy (PH), to initiate growth, protect liver cells, and sustain remnant liver functions. Extracellular adenosine triphosphate rises in blood and bile after PH and contributes to liver regeneration, although purinergic receptors and mechanisms remain to be precisely explored. In this work we analyzed during regeneration after PH the involvement of P2X4 purinergic receptors, highly expressed in the liver. P2X4 receptor expression in the liver, liver histology, hepatocyte proliferation, plasma bile acid concentration, bile flow and composition, and lysosome distribution in hepatocytes were studied in wild-type and P2X4 knockout (KO) mice, before and after PH. P2X4 receptors were expressed in hepatocytes and Kupffer cells; in hepatocytes, P2X4 was concentrated in subcanalicular areas closely costained with lysosomal markers. After PH, delayed regeneration, hepatocyte necrosis, and cholestasis were observed in P2X4-KO mice. In P2X4-KO mice, post-PH biliary adaptation was impaired with a smaller increase in bile flow and HCO3 (-) biliary output, as well as altered biliary composition with reduced adenosine triphosphate and lysosomal enzyme release. In line with these data, lysosome distribution and biogenesis were altered in P2X4-KO compared with wild-type mice., Conclusion: During liver regeneration after PH, P2X4 contributes to the complex control of biliary homeostasis through mechanisms involving pericanalicular lysosomes, with a resulting impact on hepatocyte protection and proliferation. (Hepatology 2016;64:941-953)., (© 2016 by the American Association for the Study of Liver Diseases.)

Aberrant transcriptional regulation contributes to the pathogenesis of both congenital and adult forms of liver disease. Although the transcription factor RBPJ is essential for liver morphogenesis and biliary development, its specific function in the differentiation of hepatic progenitor cells (HPC) has not been investigated, and little is known about its role in adult liver regeneration. HPCs are bipotent liver stem cells that can self-replicate and differentiate into hepatocytes or cholangiocytes in vitro. HPCs are thought to play an important role in liver regeneration and repair responses. While the coordinated repopulation of both hepatocyte and cholangiocyte compartment is pivotal to the structure and function of the liver after regeneration, the mechanisms coordinating biliary regeneration remain vastly understudied. Here, we utilized complex genetic manipulations to drive liver-specific deletion of the Rbpj gene in conjunction with lineage tracing techniques to delineate the precise functions of RBPJ during biliary development and HPC-associated biliary regeneration after hepatectomy. Furthermore, we demonstrate that RBPJ promotes HPC differentiation toward cholangiocytes in vitro and blocks hepatocyte differentiation through mechanisms involving Hippo-Notch crosstalk. Overall, this study demonstrates that the Notch-RBPJ signaling axis critically regulates biliary regeneration by coordinating the fate decision of HPC and clarifies the molecular mechanisms involved.

Background: Cholecystitis and gallstones affect a large segment of the population in developed nations, and a small proportion of affected individuals subsequently develop cancer of the gallbladder. However, little is known about the possible beneficial effects of physical activity., Objective: Accordingly, a systematic review examined the influence of both acute and chronic exercise on gallbladder motility, and relationships were examined between habitual physical activity, gallbladder disease, and gallbladder cancer., Methods: A search of Ovid/MEDLINE from 1996 to November 2014 yielded 67 articles relating to physical activity and gallbladder function or disease; 18 of these relevant to the objectives of the review were supplemented by 22 papers from personal files and other sources. Because of the limited volume of material, all were considered, although note was taken of the quality of activity measurement, care in excluding covariates, and experimental design (cross-sectional, case-control or randomized controlled trial)., Results: The impact of physical activity upon gallbladder function remains unclear; acute activity could augment emptying by stimulating cholecystokinin release, and one of two training experiments found a small increase in gallbladder motility. The largest and most recent cross-sectional and case-control trials show a reduced risk of gallbladder disease in active individuals. A small number of randomized controlled trials in humans and one animal study generally support these trends, although the number of cases of gallstones are too few for statistical significance. Three studies of gallbladder cancer also show a non-significant trend to benefit from physical activity., Conclusions: Although there remains a need for further research, regular physical activity seems likely to reduce the risk of both gallstones and gallbladder cancer. A substantial number of individuals must be persuaded to exercise in order to avoid one case of gallbladder disease, but the attempt appears warranted because of the other health benefits of regular physical activity.

The liver progenitor cell population has long been thought to exist within the liver. However, there are no standardized criteria for defining the liver progenitor cells, and there has been intense debate about the origin of these cells in the adult liver. The characteristics of such cells vary depending on the disease model used and also on the method of analysis. Visualization of three-dimensional biliary structures has revealed that the emergence of liver progenitor cells essentially reflects the adaptive remodeling of the hepatic biliary network in response to liver injury. We propose that the progenitor cell exists as a subpopulation in the biliary tree and show that the appearance of liver progenitor cells in injured parenchyma is reflective of extensive remodeling of the biliary structure., (© 2015 Japanese Society of Hepato-Biliary-Pancreatic Surgery.)

The liver has a great capacity to regenerate. Hepatocytes, the parenchymal cells of the liver, can regenerate in one of two ways: hepatocyte- or biliary-driven liver regeneration. In hepatocyte-driven liver regeneration, regenerating hepatocytes are derived from preexisting hepatocytes, whereas, in biliary-driven regeneration, regenerating hepatocytes are derived from biliary epithelial cells (BECs). For hepatocyte-driven liver regeneration, there are excellent rodent models that have significantly contributed to the current understanding of liver regeneration. However, no such rodent model exists for biliary-driven liver regeneration. We recently reported on a zebrafish liver injury model in which BECs extensively give rise to hepatocytes upon severe hepatocyte loss. In this model, hepatocytes are specifically ablated by a pharmacogenetic means. Here we present in detail the methods to ablate hepatocytes and to analyze the BEC-driven liver regeneration process. This hepatocyte-specific ablation model can be further used to discover the underlying molecular and cellular mechanisms of biliary-driven liver regeneration. Moreover, these methods can be applied to chemical screens to identify small molecules that augment or suppress liver regeneration.

Autosomal recessive polycystic kidney disease, an inherited disorder characterized by the formation of cysts in renal collecting ducts and biliary dysgenesis, is caused by mutations of the polycystic kidney and hepatic disease 1 (PKHD1) gene. Expression of PKHD1 is tissue specific and developmentally regulated. Here, we show that a 2.0-kb genomic fragment containing the proximal promoter of mouse Pkhd1 directs tissue-specific expression of a lacZ reporter gene in transgenic mice. LacZ is expressed in renal collecting ducts beginning during embryonic development but is not expressed in extrarenal tissues. The Pkhd1 promoter contains a binding site for the transcription factor hepatocyte nuclear factor (HNF)-1β, which is required for activity in transfected cells. Mutation of the HNF-1β-binding site abolishes the expression of the lacZ reporter gene in renal collecting ducts. Transgenes containing the 2.0-kb promoter and 2.7 kb of additional genomic sequence extending downstream to the second exon are expressed in the kidney, intrahepatic bile ducts, and male reproductive tract. This pattern overlaps with the endogenous expression of Pkhd1 and coincides with sites of expression of HNF-1β. We conclude that the proximal 2.0-kb promoter is sufficient for tissue-specific expression of Pkhd1 in renal collecting ducts in vivo and that HNF-1β is required for Pkhd1 promoter activity in collecting ducts. Additional genomic sequences located from exons 1-2 or elsewhere in the gene locus are required for expression in extrarenal tissues., (Copyright © 2014 the American Physiological Society.)

Purpose: To describe the patterns of bile distribution in the biliary tree, duodenum, jejunum, and stomach, and to determine the gallbladder ejection fraction (GBEF) by using functional magnetic resonance cholangiography (MRC) with gadolinium-ethoxybenzyl-diethylenetriamine penta-acetic acid (Gd-EOB-DTPA) in healthy volunteers., Materials and Methods: Forty subjects were included in this study. After conventional MRC, pre-fatty meal MRC (PRFM) was obtained at 30, 40, 50, and 60min after contrast agent injection. Then, post-fatty meal MRC (POFM) was obtained every 10min for 1h. We assessed the PRFM and POFM for opacification of contrast agent in the first- and second-order intrahepatic ducts (IHDs) and the common bile duct (CBD). Contrast agent opacification in the cystic duct was assessed, and the percentage volume of contrast agent filling in the gallbladder (GB) was calculated on PRFM. We calculated the GBEF and assessed the presence of contrast agent in the GB, duodenum, jejunum, and stomach., Results: Thirty-six (90%) subjects showed grade 3 CBD opacification (visible contrast and well-defined bile duct border) on 60-min PRFM. Thirty-four (85%) subjects showed grade 3 first-order IHD opacification on 60-min PRFM. All (100%) subjects showed cystic duct opacification of contrast agent, and the average percentage volume of contrast agent filling in the GB was 68.81%±16.84% on 60-min PRFM. The GBEF at 30-min POFM was 35.00%±18.26%. Ten (25%) subjects had no contrast agent in the stomach and small bowel on all PRFMs. Twelve (30%) subjects had contrast medium in the stomach on PRFM and/or POFM., Conclusions: Functional MRC with Gd-EOB-DTPA can allow determining the distribution of bile in the biliary tree and small intestine, as well as the GBEF., (Copyright © 2014 Elsevier Inc. All rights reserved.)

Melatonin is a widely-produced and ubiquitously-distributed molecule with multiple critical functions in all organs and organisms. These functions are mediated by both receptor-mediated and receptor-independent actions of the indole. This survey reviews the reports documenting the presence and function of melatonin in the hepatobiliary system. The published data document the exceptionally high concentrations of melatonin in the bile; herein, we speculate on the significance of these high melatonin levels to the function of the biliary tree. Moreover, we suggest that the elevated concentrations of melatonin in the bile fluid may be a consequence of its recirculation in what is referred to as the enterohepatic circulation. The article also examines the published reports related to melatonin levels in hepatocytes, which appear to be independent of pineal-derived melatonin. In both the biliary system and liver, melatonin provides protection against free radicals in cells of these organs. This is particularly important in these organs since they are under constant assault by highly toxic agents/processes that could compromise their critical physiology. As in other tissues, melatonin provides hepatocytes and cholangiocytes with a buffer against free radicals that are persistently produced and thereby this indole protects against oxidative molecular damage and metabolic dysfunction. Melatonin achieves this protection via the diverse free radical scavenging mechanisms of it and its metabolites (known as the antioxidant cascade), due to its ability to reduce electron leakage from the respiratory complexes in the inner mitochondrial membrane (radical avoidance) and as a result of the stimulation of antioxidative enzymes.

Study of biological cycles in chronic cholecystitis with dysfunction of gallbladder has a great practical importance. The results of chronoanalysis testify a dominance of 24-hours cycle in structure of cycles of functional activity of organs of hepatobiliary system. The comparative analysis of trust intervals reveals the intensification of internal connections, expressed intensification of synchronization of cycles of functional activity of system and a breach of synchronism of central regulation and self-regulation, testifying overstrain of proper adaptive possibilities and unconcordance in system of regulation. This manifestations of desynchronization provokes development and progress of dysfunction of gallbladder and dysbalance of vegetative nervous system, that make worse the present disturbances.

Notch signalling is an evolutionarily conserved intercellular pathway involved in many aspects of development and tissue renewal in several organs. The importance of Notch signalling in liver development and morphogenesis is well established. However, the post-natal role of Notch in liver repair/regeneration is only now beginning to be unveiled. Despite the simplicity of the pathway activation, a fine spatial-temporal regulation of Notch signalling is required to avoid pathologic effects. This review highlights recent advances in the field indicating that Notch signalling is involved in the reparative morphogenesis of the biliary tree and in liver carcinogenesis. Defective Notch signalling leads to impaired ability of the liver to repair liver damage, while excessive activation may be involved in liver cancer. Even though much remains to be understood about these mechanisms, including the cross-talk between Notch signalling and other liver morphogens, current evidence suggests that the modulation of the Notch pathway may represent a therapeutic target in chronic liver disease., (Copyright © 2013 Elsevier Masson SAS. All rights reserved.)

Cholangiocytes are epithelial cells that line the intra- and extrahepatic ducts of the biliary tree. The main physiologic function of cholangiocytes is modification of hepatocyte-derived bile, an intricate process regulated by hormones, peptides, nucleotides, neurotransmitters, and other molecules through intracellular signaling pathways and cascades. The mechanisms and regulation of bile modification are reviewed herein.

The process of regenerating liver is the result of a balance between stimulating factors and inhibitors of hepatocyte proliferation. Melatonin and its metabolites have been found to protect tissues against oxidative damage generated by a variety of toxic agents and metabolic processes. Furthermore, studies in liver of rats showed a decrease in the liver mitochondrial hydroxylation of drugs returning to the normal state after the administration of antioxidants. This study was designed to determine, in experimental animals, whether the administration of an antioxidant agent such as melatonin could prevent cells events leading to tissue injury and hepatic dysfunction after partial hepatectomy (PH). Biliary flow (BF), oxidative stress in hepatic tissue and Na⁺/K⁺ ATPase activities in whole plasma membrane were determined. PH decreased the Na⁺/K⁺ ATPase activity. PH significantly reduced the BF (36%) and promoted oxidative stress with an increase of lipoperoxidation and decrease of glutathione peroxidase and catalase activities. Treatment with melatonin prevented the decrease of BF in rats with hepatectomy and normalized the Na⁺/K⁺ ATPase activity. Moreover, melatonin markedly attenuated oxidative stress produced by PH. This may be the results of the higher efficacy of melatonin in scavenging various free radicals and also because of its ability in stimulating the antioxidant enzymes. We suggest that oxidative stress before and during liver regeneration has a crucial role in cholestasis, apoptotic/necrotic hepatocellular damage and the impairment in liver transport function induced by PH and that melatonin could modulate the degree of oxidative stress and through it prevent the alterations in liver function carrier., (Copyright © 2012 John Wiley & Sons, Ltd.)

The hagfish liver was histochemically examined with special attention to biliary structures around the portal veins. Hepatocytes were organized into tubular structures surrounded by sinusoids. Biliary ductule structures, which resemble the ductal plates transiently appearing in mammalian liver development, were observed around the portal veins, but they did not appear around central veins. Thus, the hagfish liver demonstrates the same basic structure as the mammalian liver; that is, a vascular system from portal to central veins via sinusoids, and portal triad structures consisting of portal veins, hepatic arteries, and intrahepatic bile ducts. The epithelial cells of the ductal platelike structures strongly expressed cytokeratin, had some lectin-binding sites, and were delineated by the basal lamina, which was reactive for periodic acid-Schiff (PAS) staining and Iectin histochemistry. The lumina of the ductal plate-like structures were comparatively small and heterogeneous in diameter around the portal veins, suggesting that the biliary structures may not be efficient for bile secretion. The epithelial cells of the gall bladder had a simple columnar shape and were a PAS-positive cytoplasm. Those of bile ducts near the hilus, including extrahepatic and hepatic ducts, were simple columnar or cuboidal cells, and had large lumina. The cytoplasm in these cells was PAS-positive. These phenotypes with the expression of lectin-binding sites were clearly different from those of the ductal plate-like structures in the liver proper, suggesting that the extrahepatic and intrahepatic biliary structures may have different developmental origins.

Stem/progenitors have been identified intrahepatically in the canals of Hering and extrahepatically in glands of the biliary tree. Glands of the biliary tree (peribiliary glands) are tubulo-alveolar glands with mucinous and serous acini, located deep within intrahepatic and extrahepatic bile ducts. We have shown that biliary tree stem/progenitors (BTSCs) are multipotent, giving rise in vitro and in vivo to hepatocytes, cholangiocytes or pancreatic islets. Cells with the phenotype of BTSCs are located at the bottom of the peribiliary glands near the fibromuscular layer. They are phenotypically heterogeneous, expressing transcription factors as well as surface and cytoplasmic markers for stem/progenitors of liver (e.g. SOX9/17), pancreas (e.g. PDX1) and endoderm (e.g. SOX17, EpCAM, NCAM, CXCR4, Lgr5, OCT4) but not for mature markers (e.g. albumin, secretin receptor or insulin). Subpopulations co-expressing liver and pancreatic markers (e.g. PDX1(+)/SOX17(+)) are EpCAM(+/-), and are assumed to be the most primitive of the BTSC subpopulations. Their descendants undergo a maturational lineage process from the interior to the surface of ducts and vary in the mature cells generated: pancreatic cells in hepatopancreatic ducts, liver cells in large intrahepatic bile ducts, and bile duct cells along most of the biliary tree. We hypothesize that there is ongoing organogenesis throughout life, with BTSCs giving rise to hepatic stem cells in the canals of Hering and to committed progenitors within the pancreas. The BTSCs are likely to be central to normal tissue turnover and injury repair and to be key elements in the pathophysiology of liver, pancreas and biliary tree diseases, including oncogenesis., (© 2011 The Authors. Journal of Anatomy © 2011 Anatomical Society.)

In this study, we investigated the expression of neuronal nitric oxide synthase (nNOS) and nicotinamide adenine dinucleotide phosphate-diaphorase (NADPH-d), two specific enzymes for nitric oxide (NO) synthesis, in the development of liver fibrosis induced by chronic bile duct ligation (BDL) in the rabbit. We specifically studied the liver-innervated nitroxidergic neurons that originate in the nodose ganglion (NG), nucleus of the solitary tract (NTS) and dorsal motor vagal nucleus (DMV). Our data showed that BDL resulted in overexpression of NADPH-d/nNOS in the NG, NTS and DMV neurons. Using densitometric analysis, we found a significant increase in NADPH-d expression as a result of BDL in the NG, NTS and DMV (72.6, 79.4 and 57.4% increase, respectively). These findings were corroborated by serum biochemistry and hepatic histopathological examination, which were influenced by NADPH-d/nNOS-generated NO in the liver following BDL. Upregulation of NADPH-d/nNOS expression may have important implications, including (1) facilitation of extrahepatic biliary parasympathetic tone that promotes gallbladder emptying of excess stagnant bile; (2) relaxation of smooth muscles of bile canaliculi thus participating in the pathogenesis of cholestasis; (3) dilation of hepatic sinusoids to counter BDL-induced intrahepatic portal hypertension in which endothelia may be damaged, and (4) alterations in hepatic metabolism, such as glycogenesis, bile formation and secretion, and bilirubin clearance., (Copyright © 2011 S. Karger AG, Basel.)

Atherosclerotic cardiovascular disease is the leading cause of morbidity and mortality in the United States and in many other countries. Dysfunctional lipid homeostasis plays a central role in the initiation and progression of atherosclerotic lesions. The ATP-binding cassette (ABC) transporters are transmembrane proteins that hydrolyze ATP and use the energy to drive the transport of various molecules across cell membranes. Several ABC transporters play a pivotal role in lipid trafficking. They are critically involved in cholesterol and phospholipid efflux and reverse cholesterol transport (RCT), processes that maintain cellular cholesterol homeostasis and protect arteries from atherosclerosis. In this article we provide a review of the current literature on the biogenesis of ABC transporters and highlight their proposed functions in atheroprotection., (Copyright © 2011. Published by Elsevier Ltd.)

Isoflurane is an inhaled halogenated hydrocarbon anesthetic commonly used for animal research. In our quest to develop a method for measuring bile acid transport in live animals using (19)F magnetic resonance (MR) imaging, it occurred to us that isoflurane, which contains five fluorines per molecule and is probably widely distributed, would provide an excellent test drug to evaluate the merits of this approach. Experiments in 20- to 28-g male C57BL/6 mice were performed using a horizontal bore scanner with a 30-mm (19)F/(1)H dual-tuned surface coil used to transmit and receive radiofrequency signals at 300.28 MHz for (1)H and 282.55 MHz for (19)F nuclei. Proton MR imaging was used to identify the mouse gallbladder in vivo, which was verified by anatomical dissection. Subsequent experiments in mice inhaling 1.5% isoflurane for 1 to 2 h revealed robust (19)F signals from the gallbladder, verified by overlying (1)H and (19)F signals. No (19)F signal was detected in mice anesthetized with nonhalogenated anesthetics. The presence of isoflurane in gallbladder bile of isoflurane-treated mice was verified using liquid chromatography-mass spectrometry. Gallbladder bile isoflurane content ranged from 3.2 to 4.7 μg. The data presented here provide proof of concept that this novel approach can be used for in vivo measurement of biliary excretion of both existing and novel (19)F-labeled drugs.

Micafungin, a new echinocandin antifungal agent, has been used widely for the treatment of various fungal infections in human populations. Micafungin is predominantly cleared by biliary excretion and it binds extensively to plasma proteins. Micafungin body weight-adjusted clearance is higher in neonates than in adults, but the mechanisms underlying this difference are not understood. Previous work had revealed the roles of sinusoidal uptake (Na(+) -taurocholate co-transporting peptide, NTCP; organic anion transporting polypeptide, OATP) as well as canalicular efflux (bile salt export pump, BSEP; breast cancer resistance protein, BCRP) transporters in micafungin hepatobiliary elimination. In the present study, the relative protein expression of hepatic transporters was compared between liver homogenates from neonates and adults. Also, the extent of micafungin binding to serum from neonates and adults was measured in vitro. The results indicate that relative expression levels of NTCP, OATP1B1/3, BSEP, BCRP and MRP3 were similar in neonates and in adults. However, the micafungin fraction unbound (f(u) ) in neonatal serum was about 8-fold higher than in the adult serum (0.033±0.012 versus 0.004±0.001, respectively). While there was no evidence for different intrinsic hepatobiliary clearance of micafungin between neonates and adults, our data suggest that age-dependent serum protein binding of micafungin is responsible for its higher clearance in neonates compared with adults., (Copyright © 2011 John Wiley & Sons, Ltd.)

Animal model phenotyping, in utero exposure toxicity studies, and investigation into causes of embryonic, fetal, or perinatal deaths have required pathologists to recognize and diagnose developmental disorders in spontaneous and engineered mouse models of disease. In mammals, the liver is the main site of hematopoiesis during fetal development, has endocrine and exocrine functions important for maintaining homeostasis in fetal and adult life; and performs other functions including waste detoxification, production and removal of glucose, glycogen storage, triglyceride and fatty acid processing, and serum protein production. Due to its role in many critical functions, alterations in the size, morphology, or function(s) of the liver often lead to embryonic lethality. Many publications and websites describe individual aspects of hepatobiliary development at defined stages. However, no single resource provides a detailed histological evaluation of H&E-stained sections of the developing murine liver and biliary systems using high-magnification and high-resolution color images. The work herein provides a histology atlas of hepatobiliary development between embryonic days 9.5-18.5. Although the focus of this work is normal hepatobiliary development, common defects in liver development are also described as a reference for pathologists who may be asked to phenotype mice with congenital, inherited, or treatment-related hepatobiliary defects. Authors' note: All digital images can be viewed online at https://niehsimagesepl-inc.com with the username "ToxPathLiver" and the password "embryolivers."

An obstructed biliary system is usually drained by endoscopic retrograde cholangiopancreatography, and when this is unsuccessful, the standard alternative technique is percutaneous transhepatic biliary drainage. Surgical biliary bypass may also be required. In recent years, endosonography has transformed from a solely diagnostic procedure to one with therapeutic capabilities. Endosonography-guided biliary drainage is now being performed as an alternative to percutaneous transhepatic biliary drainage. This is an evolving field, with challenges that must be addressed before it can become a routine clinical practice. This review summarises the current status of endosonography-guided biliary drainage.

Objective: To investigate the effect on intrahepatic cholangiocytes mediated by hypoxic preconditioning (HP) after liver transplantation and the role of vascular endothelial growth factor (VEGF)., Materials and Methods: This experiment was based on a model of rat orthotopic liver autotransplantation. Sprague-Dawley rats were randomly divided into 3 groups: normal control, autotransplantation (AT), and HP. The HP group was subjected to 8% oxygen atmosphere for 90 minutes before surgery. At 6, 12, 24, and 48 hours after autotransplantation, the rats were killed for testing .Serum total bilirubin, direct bilirubin, and alkaline phosphatase concentrations were determined. The microstructure of cholangiocytes and the ultramicrostructure of cholangioles were determined. Immunohistochemistry was used to detect the expression of VEGF and the proliferation rate of cholangiocytes., Results: Total bilirubin, direct bilirubin, and alkaline phosphatase concentrations in the AT group increased considerably more than in the HP group during the entire interval (P < .05). Light microscopy demonstrated that the microstructure of cholangiocytes in the AT group was damaged more seriously than in the HP group. At transmission electron microscopy, the ultramicrostructure of cholangioles was changed more obviously than in the HP group. The expression of VEGF on cholangiocytes and the proliferation rate of cholangiocytes were higher in the HP group than in the AT group over the entire experiment (P < .05)., Conclusion: Hypoxic preconditioning has a protective effect on cholangiocytes after liver autotransplantation. The mechanism may be related to HP-induced overexpression of VEGF on cholangiocytes., (2010 Elsevier Inc. All rights reserved.)

The results of experimental investigation of peculiarities of morphological transformation course in autotissues under the influence of bile were adduced. There was proposed a choice of peritoneum as an optimal plastic material in conditions of possible deficiency of local tissues during biliary surgery performance.

Objectives: The objective of this study was to explore the effect of various bile duct flush (BDF) solutions on biliary tract preservation of donated livers in rats., Methods: We studied the effects of BDF solutions and cold ischemic times on biliary tract preservation, using 2 kinds of solutions: (1) BDFa with normal saline (NS), or hypertonic citrate-adenine kidney preservation in vivo (HCA), and (2) BDFb with University of Wisconsin solution (UW), or histidine-tryptophan-ketoglutarate solution (HTK). The cold ischemic times (CIT) were 4, 8, or 12 hours. Forty-five healthy male Wistar rats were randomly divided into 9 groups of 5 rats each using a [L(9)(3(4))] orthogonal table. Biliary tract tissues were examined at the corresponding cold preservation times for the following: microscopic changes in bile duct cells; TUNEL (Transferase-mediated, dUTP-bitin nick end labeling) procedure assays apoptotic indices (AI) of endothelial cells in the biliary tract; ultrastructural changes; and average volumes (V) and density (Nd) of mitochondria in endothelial cells calculated using an image analysis system. The results were evaluated by analysis of variance (ANOVA) and direct analysis by an orthogonal design., Results: AI of biliary tract endothelial cells showed significance (P < .01) of cold preservation of the biliary tract of donor liver with BDFa or BDFb and CIT; furthermore, HCA, HTK, and 4-hour CIT were all ideal. V and Nd of mitochondrial endothelial cells were significantly increased (P < .01) with BDFa, BDFb, and CIT; furthermore, factors HCA, HTK, and 4-hour CIT were all ideal., Conclusions: Cold preservation injuries to the biliary tract of a donor liver may be greatly decreased by efficient and sufficient flushing of the bile tract. A suitable bile duct solution greatly decreases cold preservation injuries and protects endothelial cells.

The biliary tree system consists of two divisions: intrahepatic bile ducts and extrahepatic bile ducts. The development of the biliary tree, and secondarily the liver, shares a common origin with ventral pancreas. A common progenitor for liver, biliary duct system, and ventral pancreas exists at early stages of development, when the anterior definitive endoderm is forming the foregut. Several studies indicate that the biliary tree contains stem cell compartments for liver, pancreas and the bile duct system and persisting into adulthood. These stem cell compartments are present in the peribiliary glands and possibly give rise to committed progenitors in gallbladder that does not have peribiliary glands. The biliary tree stem/progenitors represent a new source of cells that can be used as tools for regenerative medicine of liver, bile duct and pancreas.

Background and Purpose: It has been suggested that liver regeneration can occur either by differentiated adult hepatocytes which retain the capability for several rounds of replication or by hepatic progenitor cells, depending on the number of hepatocytes lost. We sought to study the differentiation potential of hepatocytes following partial hepatectomy (PH) in rats., Methods: Using immunohistochemistry and confocal microscopy we studied the distribution of cytokeratin 7 (CK7), CK19, vimentin, desmin, CD34, and c-kit among adult rat liver hepatocytes after PH at various times just after hepatectomy and after 8, 16, 24, 36, 48, and 60 hour and 6 and 16 days., Results: Vimentin, c-kit, and desmin positivity were observed in regenerating hepatocytes in the early stages. Desmin and vimentin staining were also demonstrated in stellate cells. Staining enhancement in stellate cells progressed from day 3 to day 6. No liver sections were stained positive for CD34, CK19, or CK7., Conclusion: After PH, mature hepatocytes revealed their potential to regain the markers that they do not express when they are quiescent. This result supported the plasticity and differentiation potential of adult hepatocytes during regeneration.

In the liver, adenosine triphosphate (ATP) is an extracellular signaling molecule that is released into bile and stimulates a biliary epithelial cell secretory response via engagement of apical P2 receptors. The molecular identities of the ion channels involved in ATP-mediated secretory responses have not been fully identified. Intermediate-conductance Ca(2+)-activated K(+) channels (IK) have been identified in biliary epithelium, but functional data are lacking. The aim of these studies therefore was to determine the location, function, and regulation of IK channels in biliary epithelial cells and to determine their potential contribution to ATP-stimulated secretion. Expression of IK-1 mRNA was found in both human Mz-Cha-1 biliary cells and polarized normal rat cholangiocyte (NRC) monolayers, and immunostaining revealed membrane localization with a predominant basolateral signal. In single Mz-Cha-1 cells, exposure to ATP activated K(+) currents, increasing current density from 1.6 +/- 0.1 to 7.6 +/- 0.8 pA/pF. Currents were dependent on intracellular Ca(2+) and sensitive to clotrimazole and TRAM-34 (specific IK channel inhibitors). Single-channel recording demonstrated that clotrimazole-sensitive K(+) currents had a unitary conductance of 46.2 +/- 1.5 pS, consistent with IK channels. In separate studies, 1-EBIO (an IK activator) stimulated K(+) currents in single cells that were inhibited by clotrimazole. In polarized NRC monolayers, ATP significantly increased transepithelial secretion which was inhibited by clotrimazole. Lastly, ATP-stimulated K(+) currents were inhibited by the P2Y receptor antagonist suramin and by the inositol 1,4,5-triphosphate (IP3) receptor inhibitor 2-APB. Together these studies demonstrate that IK channels are present in biliary epithelial cells and contribute to ATP-stimulated secretion through a P2Y-IP3 receptor pathway.

The anion gap (AG) measurement is a very useful tool in the evaluation of patients with acid-base disorders. Once metabolic acidosis is identified, AG will provide the important first step in the differential diagnosis of disorders that either increase the AG and those that leave the AG unchanged. Delta gap is the comparison between change (delta) in the AG and the change (delta) in bicarbonate (HCO(3)(-)). Delta ratio, defined as delta AG:delta HCO(3)(-) is usually 1:1 in patients with an uncomplicated high AG acidosis. A value below 1:1 suggests a combined high and normal AG acidosis. A value above 2:1 suggests a combined metabolic alkalosis and a high AG acidosis. Urine AG (unmeasured anions-unmeasured cations) is an indirect estimate of the urine NH(4)(+) excretion. It is typically negative in patients with normal AG metabolic acidosis secondary to diarrhoea. Utilisation of AG calculations helps clinicians in identifying and treating acid-base disorders.

The treatment of diabetes by islet transplantation is presently hampered by the shortage of organ donors. The generation of insulin-producing cells is therefore a major objective in the long-term goal of curing diabetes. Alternative sources of pancreatic beta-cells include existing pancreatic cells, embryonic stem cells, and cells from other tissues such as liver. This commentary considers evidence for two new sources of beta-cells: intrahepatic biliary epithelial cells and gall bladder epithelium. These observations raise the possibility that a patient's own cells may be used as a source of insulin-producing cells for cell replacement in diabetes.

The liver plays a key role in the metabolic conversion and elimination of endo- and xenobiotics. Hepatobiliary transport of many of these compounds is mediated by several ATP-binding cassette (ABC) transporters expressed at the canalicular membrane of the hepatocyte. Impaired function of these ABC transporters leads to impaired bile formation or cholestasis and mutations in these genes are associated with a variety of hereditary cholestatic syndromes. At the transcriptional level, these ABC transporters and the metabolizing enzymes involved in processing of their substrates are coordinately regulated by members of the nuclear receptor (NR) family of ligand-modulated transcription factors. In this review we will focus on ABC transporters involved in hepatobiliary excretion and how they are associated with hepatic physiology and disease states. We will also examine how NRs, acting as intracellular sensors for lipophilic molecules, regulate these ABC transporters and maintain metabolic homeostasis.

Multidrug-resistant protein 2 (MRP2/ABCC2), expressed on the canalicular membrane of hepatocytes, mediates the secretion of conjugated or nonconjugated compounds into bile and plays an important role in physiology and drug elimination. A heterocyclic compound, BPCPU [1-(1-(4-bromophenyl)-3-carbamoyl-1H-pyrazol-4-yl) urea], which was metabolically stable in vitro in rat liver microsomes and freshly isolated rat hepatocytes, demonstrated a saturable nonlinear pharmacokinetic profile in the rat. Polarized efflux was observed for this compound in Caco-2 cells, with a low K(m) = 1.06 +/- 0.06 microM. The Caco-2 efflux was dose-dependent and saturable. Coadministration of 25 microM MK571 ([3-[[3-[2-(7-chloroquinolin-2-yl)vinyl]phenyl]-(2-dimethylcarbamoylethylsulfanyl)methylsulfanyl] propionic acid]), an MRP inhibitor, blocked the polarized efflux in Caco-2 cells. In contrast, this compound did not inhibit calcein efflux in MRP2 gene-transfected Madin-Darby canine kidney cells, suggesting that it is a substrate, not an inhibitor, of the MRP2/ABCC2 transporter. To investigate the mechanism for the nonlinear pharmacokinetics, bile duct-cannulated rats were used to obtain time profiles of plasma concentration, biliary, and urinary excretion after intravenous administration at various doses. The plasma clearance increased remarkably with decreased dose, from 1.5 ml/min/kg at 5 mg/kg to 14.9 ml/min/kg at 0.05 mg/kg. A dose-dependent biliary excretion also was observed. The results revealed that saturation of hepatobiliary secretion played a role in the dose-dependent changes in total body clearance and biliary clearance. Saturating concentrations of the Mrp2/Abcc2 substrate, BPCPU, causing decreased hepatobiliary clearance could be the major cause for the nonlinear pharmacokinetics observed in rats.