Quantitative changes in acid phosphatase, alkaline phosphatase and 5'-nucleotidase activity in rat liver after experimentally induced cholestasis

Therapeutic Potential of Cucumis melo (L.) Fruit Extract and Its Silver Nanopartciles Against DEN-Induced Hepatocellular Cancer in Rats

Biosynthesized silver nanoparticles have a wide range of biological activities and using nanoparticles as one of the novel approaches in cancer therapy. In this present research work, the anti-cancer efficacy of Cucumis melo fruit extract and its silver nanoparticles was explored. Wistar rats were divided into six groups and hepatic cancer was induced with 0.01% DEN (diethylnitrosamine) through drinking water for 16 weeks. Cyclophosphamide was given as the standard drug at the dose of 50 mg/kg body weight. Hematological parameters showed a decrease in the levels of hemoglobin (Hb), packed cell volume (PCV), red blood cells (RBC), mean corpuscular volume (MCV), mean corpuscular Hb (MCH), mean corpuscular Hb concentration (MCHC), and platelets (PLTS) levels except white blood cell (WBC) in DEN-induced cancer animals. Significant alterations in the hematological parameters were observed after treatment which indicate the protective effect of Cucumis melo fruit on the hemopoietic system. The structural integrity of the cells has been damaged in cancer-induced animals, and this results in cytoplasmic leakage of enzyme into the blood stream, leads to the elevated levels of these enzymes in blood with subsequent fall in the tissues. Hence, the levels of liver function markers such as AST ALT, ALP, LDH, GGT, and 5'NT were significantly elevated in serum and the liver of cancer-induced rats. The levels of serum tumor markers, viz., alpha-fetoprotein (AFP) and carcinoembryonic antigen (CEA), elevated in rats induced with DEN, which then were reduced following Cucumis melo fruit treatment, indicating the anti-cancer activity of the drug. Histological evaluation of the liver and kidney was also performed to authenticate the present work. Treatment with crude extract and silver nanoparticles of Cucumis melo fruit indicates that Cucumis melo fruit could have exerted its protective effect.

Effect of consumption of whole egg and egg fractions on cardiovascular disease factors in adult rats

BACKGROUND

While eggs are a low-cost source of protein, rich in macro- and micronutrients, the association of egg intake and cardiovascular disease (CVD) remains controversial. This study investigated the effect of egg consumption on CVD parameters. Eggs were boiled, separated into four fractions (whole egg, 50% yolk-reduced whole egg, egg yolk and egg white) and then freeze-dried. The different egg fractions or distilled water (control) were orally gavaged to adult male Wistar rats at 1 g kg^-1 rat body weight, each day for 8 weeks, following which basal blood pressure, heart rate, complete blood cell count, blood biochemistry, body fat and liver cell lipid accumulation were determined. The vascular functions of isolated thoracic aorta were studied using classical pharmacological techniques.

RESULTS

In comparison to the control group, none of the egg fractions affected body weight, food intake, plasma glucose or lipid profile. The yolk group experienced increased plasma alkaline phosphatase and creatinine levels, while egg white caused decreased plasma cholesterol and blood urea nitrogen. Whole egg and egg yolk increased blood pressure and mean hemoglobin concentration and the yolk increased liver lipid accumulation. Egg white decreased the white blood cell count and body fat lipids. No changes were found in basal heart rate or vascular functions in any of the groups.

CONCLUSIONS

Consumption of whole egg or egg yolk at the dosage given caused hypertension, with impairment of liver and kidney functions following the intake of yolk alone. However, egg white is beneficial for the cardiovascular system as it decreased plasma cholesterol and body fat accumulation. © 2020 Society of Chemical Industry.

Assessment of the Antitumor Potentiality of Newly Designed Steroid Derivatives: Pre-Clinical Study

Cancer is recognized as one of the most prevalent contributors to mortality in several nations and it remains one of the common health issues globally. In particular, hepatocellular carcinoma (HCC) has become a public health problem along with the increase of hepatitis B (HBV) and hepatitis C (HCV) virus infections. Based on this fact, our study goaled to synthesize newly hybrid drugs containing heterocyclic rings incorporated to steroid moiety and to examine the potential antitumor activity of the newly designed heterosteroid derivatives against HCC induced in animal model. Several heterocyclic steroids were synthesized 2-7 and confirmed via the analytical and spectral data (IR, ¹H NMR¹³C NMR and Mass spectroscopy). Compounds 3, 4, and 5 were chosen to be investigated as anticancer agents in HCC rat model by means of validated biomarkers (alfa –fetoprotein, endoglin, lipocali-2 and heat shock protein-70). Following administration of compounds 3, 4 or 5, availability of the active tumor marker molecules was significantly dropped and a substantial decrease of the angiogenic and inflammatory mediators was also evident. These findings were supported by the histological examination of liver tissue. Taken together, this study indicates the potential anticancer activity of the newly synthesized heterosteroid derivatives against HCC in vivo. The antitumor activity of these compounds was likely attributable to modulating some signal transduction pathways involved in tumorigenesis, angiogenesis and inflammation.

Ablation of hepatic malignant tumors with irreversible electroporation: A systematic review and meta-analysis of outcomes

Background

Irreversible electroporation (IRE) ablation is a new technique that is used to eliminate malignant tumors through nonthermal approaches.

Objective

The purpose of this review was to evaluate the efficiency of IRE for hepatic malignant tumors.

Methods

A systematic search was performed from PubMed, Embase, Web of science, Scopus and other potential literatures from references in relevant articles July 26th, 2016. Overall estimates of pooled standard mean difference (SMD) with 95% confidence interval (CI) were calculated for the changes of the pre- and post-IRE longest diameter, alkaline phosphatase (ALP), aspartate aminotransferase (AST) and serum total bilirubin levels. Sensitivity analysis and publication bias and were performed after the pooled analysis, and the quality of the included literatures was appraised using Newcastle-Ottawa Scale (NOS).

Results

We finally included 300 patients (mean age: 51 to 66.6 years; male: 182; female: 118) from 9 studies of hepatic malignant tumors. The meta-analysis showed that comparing with the initial values, the longest diameter of the tumors was significantly decreased at the last follow-up months after IRE. Furthermore, the ALP, AST and total bilirubin levels were increased at 1 day after IRE while returned to baseline at the last follow-up month. No risk of publication bias was found, and all literatures were assessed good quality according to NOS.

Conclusions

The pooled data indicated that IRE could be a minimal invasive and effective approach for patients who had preoperative poor liver function or those whose masses were in refractory locations where surgical resection was unsuitable.

Antitumor Effect of the Mannich Base(1,3-bis-((3-Hydroxynaphthalen-2-yl)phenylmethyl)urea) on Hepatocellular Carcinoma

The present study was designed to evaluate the antitumor effects of the synthetic Mannich base 1,3-bis-((3-hydroxynaphthalen-2-yl)phenylmethyl)urea (1,3-BPMU) against HEP-G2 hepatoma cells and diethylnitrosamine (DEN)-induced hepatocarcinoma (HCC) in albino rats. In vitro analysis results revealed that 1,3-BPMU showed significant cytotoxicity and cell growth inhibition in HEP-G2 hepatoma cells in a concentration-dependent manner. Furthermore, flow cytometry results indicated that 1,3-BPMU enhanced early and late apoptosis. The maximum apoptosis was exhibited at a concentration of 100 μg/mL of 1,3-BPMU. In in vivo analysis, DEN treatment increased the content of nucleic acids, LPO and the activities of AST, ALT, ALP, LDH, γGT and 5'NT with decreased antioxidant activity as compared to control rats. However, 1,3-BPMU treatment to DEN-induced rats decreased the content of nucleic acids, LPO and the activities of AST, ALT, ALP, LDH, γGT and 5'NT and increased the activities of SOD, CAT, GPx, GST and GR (p < 0.05). Furthermore, 1,3-BPMU enhanced the apoptosis via upregulation of caspase-3 and caspase-9 and the downregulation of Bcl-2 and Bcl-XL mRNA expression as compared to DEN-induced rats. Histological and ultrastructural investigation showed that 1,3-BPMU treatment renovated the internal architecture of the liver in DEN-induced rats. In this study, the molecular and pre-clinical results obtained by treatment of DEN-induced rats with 1,3-BPMU suggested that 1,3-BPMU might be considered as an antitumor compound in the future.

Altered alkaline phosphatase activity in obese Zucker rats liver respect to lean Zucker and Wistar rats discussed in terms of all putative roles ascribed to the enzyme

Biliary complications often lead to acute and chronic liver injury after orthotopic liver transplantation (OLT). Bile composition and secretion depend on the integrated action of all the components of the biliary tree, starting from hepatocytes. Fatty livers are often discarded as grafts for OLT, since they are extremely vulnerable to conventional cold storage (CS). However, the insufficiency of donors has stimulated research to improve the usage of such marginal organs as well as grafts. Our group has recently developed a machine perfusion system at subnormothermic temperature (20°C; MP20) that allows a marked improvement in preservation of fatty and even of normal rat livers as compared with CS. We sought to evaluate the response of the biliary tree of fatty liver to MP20, and a suitable marker was essential to this purpose. Alkaline phosphatase (AlkP, EC 3.1.3.1), frequently used as marker of membrane transport in hepatocytes and bile ducts, was our first choice. Since no histochemical data were available on AlkP distribution and activity in fatty liver, we have first settled to investigate AlkP activity in the steatotic liver of fatty Zucker rats (fa/fa), using as controls lean Zucker (fa/+) and normal Wistar rats. The AlkP reaction in Wistar rats was in accordance with the existing data and, in particular, was present in bile canaliculi of hepatocytes in the periportal region and midzone, in the canals of Hering and in small bile ducts but not in large bile ducts. In lean ZR liver the AlkP reaction in Hering canals and small bile ducts was similar to Wistar rat liver but hepatocytes had lower canalicular activity and besides presented moderate basolateral reaction. The difference between lean Zucker and Wistar rats, both phenotypically normal animals, could be related to the fact that lean Zucker rats are genotypically heterozygous for a recessive mutated allele. In fatty liver, the activity in ductules and small bile ducts was unchanged, but most hepatocytes were devoid of AlkP activity with the exception of clusters of macrosteatotic hepatocytes in the mid-zone, where the reaction was intense in basolateral domains and in distorted canaliculi, a typical pattern of cholestasis. The interpretation of these data was hindered by the fact that the physiological role of AlkP is still under debate. In the present study, the various functions proposed for the role of the enzyme in bile canaliculi and in cholangiocytes are reviewed. Independently of the AlkP role, our data suggest that AlkP does not seem to be a reliable marker to study the initial step of bile production during OLT of fatty livers, but may still be used to investigate the behaviour of bile ductules and small bile ducts.

Altered membrane glycoprotein targeting in cholestatic hepatocytes

BACKGROUND

Hepatocytes are polarized epithelial cells with three morphologically and functionally distinct membrane surfaces: the sinusoidal, lateral and canalicular surface domains. These domains differ from each other in the expression of integral proteins, which concur to their polarized functions. We hypothesize that the cholestasis-induced alterations led to partial loss of hepatocyte polarity. An altered expression of membrane proteins may be indicative of functional disorders. Alkaline liver phosphatase (ALP), one of the most representative plasma membrane glycoproteins in hepatocytes, is expressed at the apical (canalicular) pole of the cell. Because the release of ALP protein in the bloodstream is significantly increased in cholestasis, the enzymatic levels of plasma ALP have major relevance in the diagnosis of cholestatic diseases. Here we assess the cholestasis-induced redistribution of membrane glycoproteins to investigate the ALP release.

MATERIALS AND METHODS

We performed enzymatic histochemistry, immunohistochemistry, lectin histochemistry, immunogold and lectin-and immunoblotting studies. Experimental cholestasis was induced in rats by ligation of common bile duct (BDL).

RESULTS

The BDL led to altered membrane sialoglycoprotein targeting as well as to ultrastructural and functional disorders. Disarrangement of the microtubular system, thickening of the microfilamentous pericanalicular ectoplasm and disturbance of the vectorial trafficking of membrane glycoprotein containing vesicles were found.

CONCLUSIONS

Altogether, results indicate that the cholestasis-induced partial loss of hepatocyte cell polarity leads to mistranslocation of ALP to the sinusoidal plasma membrane from where the enzyme is then massively released into the bloodstream.

Dehydroepiandrosterone supplement increases malate dehydrogenase activity and decreases NADPH-dependent antioxidant enzyme activity in rat hepatocellular carcinogenesis

Beneficial effects of dehydroepiandrosterone (DHEA) supplement on age-associated chronic diseases such as cancer, cardiovascular disease, insulin resistance and diabetes, have been reported. However, its mechanism of action in hepatocellular carcinoma in vivo has not been investigated in detail. We have previously shown that during hepatocellular carcinogenesis, DHEA treatment decreases formation of preneoplastic glutathione S-transferase placental form-positive foci in the liver and has antioxidant effects. Here we aimed to determine the mechanism of actions of DHEA, in comparison to vitamin E, in a chemically-induced hepatocellular carcinoma model in rats. Sprague-Dawley rats were administered with control diet without a carcinogen, diets with 1.5% vitamin E, 0.5% DHEA and both of the compounds with a carcinogen for 6 weeks. The doses were previously reported to have anti-cancer effects in animals without known toxicities. With DHEA treatment, cytosolic malate dehydrogenase activities were significantly increased by ~5 fold and glucose 6-phosphate dehydrogenase activities were decreased by ~25% compared to carcinogen treated group. Activities of Se-glutathione peroxidase in the cytotol was decreased significantly with DHEA treatment, confirming its antioxidative effect. However, liver microsomal cytochrome P-450 content and NADPH-dependent cytochrome P-450 reductase activities were not altered with DHEA treatment. Vitamin E treatment decreased cytosolic Se-glutathione peroxidase activities in accordance with our previous reports. However, vitamin E did not alter glucose 6-phosphate dehydrogenase or malate dehydrogenase activities. Our results suggest that DHEA may have decreased tumor nodule formation and reduced lipid peroxidation as previously reported, possibly by increasing the production of NADPH, a reducing equivalent for NADPH-dependent antioxidant enzymes. DHEA treatment tended to reduce glucose 6-phosphate dehydrogenase activities, which may have resulted in limited supply for de novo synthesis of DNA via inhibiting the hexose monophophaste pathway. Although both DHEA and vitamin E effectively reduced preneoplastic foci in this model, they seemed to function in different mechanisms. In conclusion, DHEA may be used to reduce hepatocellular carcinoma growth by targeting NADPH synthesis, cell proliferation and anti-oxidant enzyme activities during tumor growth.

A toxicologist guide to the diagnostic interpretation of hepatic biochemical parameters

Assessing liver damage in basic toxicology research and in preclinical toxicity testing is usually evaluated by serum biochemical parameters prior to confirmation by histopathology. With the advent of newer methods such as genomics and proteomics, there is increased enthusiasm to generate "novel" predictive markers to detect liver pathology even before the alterations in clinical and histopathology parameters occur. However, serum biochemical parameters (clinical pathology) when employed accurately, can provide important and useful information in assessing not only the extent and severity of liver damage, but also the type of liver damage (membrane injury versus cholestasis and hepatic function). In order to accurately detect hepatobiliary pathologies, it is important to have a basic understanding of liver associated clinical pathology parameters with reference to their exact location, serum half-lives, tissue concentration gradient and species differences. Such understanding as discussed in this article will enable a toxicologist to identify commonly encountered toxic hepatic lesions such as necrosis, cholestasis and compromised liver function by hepatic-associated clinical pathology parameters. In addition, toxicologists will have a better grasp to effectively communicate their clinical pathology findings and interpretations to the target audiences.

The activity of ornithine transcarbamoylase and arginase during mechanical jaundice in the rat model

BACKGROUND

The pathogenesis of morbidity and mortality associated with intervention of the biliary system in patients with obstructive jaundice is unknown. Mechanical jaundice initiates the development of morphological changes in hepatocytes with concomitant disturbances in metabolism. These are followed by changes in enzyme activity in hepatocytes and peripheral blood.

MATERIAL AND METHODS

Wistar rats were divided into three groups: group 1, sham-operated controls; group 2, rats with permanent jaundice; and group 3, rats with temporary mechanical jaundice. The animals were examined at 2 weeks (groups A), 4 weeks (groups B) and 6 weeks (groups C) after surgery. We explored the impact of induced mechanical jaundice on the activity of selected urea cycle enzymes (arginase [E.C.3.5.3.1] and ornithine transcarbamoylase (OTC) [E.C.2.1.3.3]).

RESULTS

Mechanical jaundice was found to induce changes in hepatocytic metabolism, which in turn led to disturbances in the urea cycle and the process of transamination. After relief of the mechanical jaundice (recanalization of the common bile duct), the urea cycle activity in the liver was greatly increased despite the normalization of the basic biochemical indices.

CONCLUSION

The results of the experiment confirmed the hypothesis that long-term mechanical jaundice causes lasting disturbances in hepatocytic metabolism. We conclude that the rate of nitrogen metabolism is higher after recanalization of the bile duct.

The involvement of altered vesicle transport in redistribution of Ca2+, Mg2+-ATPase in cholestatic rat liver

Vectorial sorting of plasma membrane protein-containing vesicles is essential for the establishment and maintenance of cell polarity. In the present study, the involvement of altered vesicle transport in the redistribution of membrane-bound Ca2+, Mg2+-ATPase resulting from cholestasis was investigated in hepatocytes. Cholestasis was induced in rat liver by common bile duct ligation. Ca2+, Mg2+-ATPase activity was demonstrated histochemically at the light and electron microscopical levels. Microtubules, an important factor for transcellular transport of vesicles, were studied in situ by immunofluorescence microscopy and electron microscopy in detergent-extracted preparations. The results showed that microtubules underwent significant changes after common bile duct ligation. The most pronounced alteration was focal accumulation of beta-tubulin in the cytoplasm of hepatocytes after 7 days of common bile duct ligation. At the electron microscopical level, the number of microtubules was increased considerably. In control livers, the activity of Ca2+, Mg2+-ATPase was localized only at the apical plasma membrane of hepatocytes, but it was also present at the basolateral plasma membrane after common bile duct ligation. The number of intracellular vesicles containing Ca2+, Mg2+-ATPase activity was increased strikingly, and some of them were associated with lateral membrane domains in which Ca2+, Mg2+-ATPase activity was found. It is concluded that common bile duct ligation induces the rearrangement of microtubules, which may disturb vectorial transport of Ca2+, Mg2+-ATPase-containing vesicles in hepatocytes, leading to the redistribution of Ca2+, Mg2+-ATPase.

Phosphohydrolytic activity in Paramecium caudatum at neutral pH

Phosphohydrolytic activity was cytochemically characterized in Paramecium caudatum, a ciliated protozoa, at neutral pH. We stained cells in the presence of several mononucleotides as substrates, namely adenosine 5'-monophosphate (5'-AMP), adenosine 2'-monophosphate, guanosine 5'-monophosphate (5'-GMP) and beta-glycerophosphate (beta-GLP) using a lead capture method at 37 degrees C. Cells were also incubated in the presence of 5'-AMP with the inhibitor for alkaline phosphatase, tetramisole. In all cases, varying amounts of final reaction product, lead sulfide, was observed in Paramecium cytoplasm. Tetramisole did not have any effect on Paramecium 5'-AMP hydrolytic activity. The phosphohydrolytic activity was measured as the increase in total absorbance of "test minus control" reactions at 440 nm per unit time after 20 min of incubation using a microphotometric system for image analysis that has been developed by us. From the relationship between the concentrations of 5'-AMP and activity, an apparent K(m) value was estimated to be 0.20 mM. These results suggest that mononucleotides and phosphate monoesters are hydrolyzed by one or more enzymes with wide substrate specificity in P. caudatum. All the activity distribution patterns in Paramecium cultures, that were tested, were monomodal. The mean activity for 5'-AMP hydrolysis widely varied in these cultures. To investigate substrate affinity, distribution patterns and mean activity with 5'-AMP as substrate were compared with those in the presence of 2 other substrates, 5'-GMP and beta-GLP. Affinity of the enzyme(s) was similar for 5'-AMP and 5'-GMP and lower for beta-GLP.

Current concepts of hepatic uptake, intracellular transport and biliary secretion of bile acids: physiological basis and pathophysiological changes in cholestatic liver dysfunction

Hepatic sinusoidal uptake of bile acids is mediated by defined carrier proteins against unfavourable concentration and electrical gradients. Putative carrier proteins have been identified using bile acid photoaffinity labels and more recently using immunological probes, such as monoclonal antibodies. At the sinusoidal domain, proteins with molecular weights of 49 and 54 kDa have been shown to be carriers for bile acid transport. The 49 kDa protein has been associated with the Na(+)-dependent uptake of conjugated bile acids, while the 54 kDa carrier has been involved in the Na(+)-independent bile acid uptake process. Within the hepatocyte, cytosolic proteins, such as the glutathione S-transferase (also designated the Y protein), the Y binders and the fatty acid binding proteins, are able to bind bile acids and possibly facilitate their movement to the canalicular domain. At the canalicular domain a 100 kDa carrier protein has been isolated and it has been shown by several laboratories that this particular protein is concerned with canalicular bile acid transport. The system is ATP-dependent and follows Michaelis-Menten kinetics. Interference with bile acid transport has been demonstrated by several chemicals. The mechanisms by which these chemicals inhibit bile acid transport may explain the apparent cholestatic properties observed in patients and experimental animals treated with these agents. Several studies have shown that Na+/K(+)-ATPase activity is markedly decreased in cholestasis induced by ethinyloestradiol, taurolithocholate and chlorpromazine. However, other types of interference have been described and the cholestatic effects may be the result of several mechanisms. Cholestasis is associated with several adaptive changes that may be responsible for the accumulation of bile acids and other cholephilic compounds in the blood of these patients. It may be speculated that the nature of these changes is to protect liver parenchymal cells from an accumulation of bile acids to toxic levels. However, more detailed quantitative experiments are necessary to answer questions with regard to the significance of these changes and the effect of various hepatobiliary disorders in modifying these mechanisms. It is expected that the mechanisms by which bile acid transport is regulated and efforts to understand the molecular basis for these processes will be among the areas of future research.

Heterogeneity of kinetic parameters of enzymes in situ in rat liver lobules

In the present review, metabolic compartmentation in liver lobules is discussed as being dynamic and more complex than thus far assumed on the basis of numbers of mRNA or protein molecules or the capacity (zero-order activity) of enzymes. Isoenzyme distribution patterns and local kinetic parameters of enzymes may vary over the different zones of liver lobules. As a consequence, metabolic fluxes in vivo at physiological substrate concentrations may be completely different from those that are assumed on the basis of the number of molecules or the capacity of enzymes present in zones of liver lobules. For a more correct estimation of the levels of metabolic processes in the different compartments of liver tissue, local kinetic parameters and substrate concentrations have to be determined to calculate local metabolic fluxes. Direct measurements of metabolic fluxes in vivo with the use of noninvasive techniques is a promising alternative and the techniques will become increasingly important in future metabolic research.

G proteins in rat liver proliferation during cholestasis

Liver proliferation appears to be dually regulated, in part by cyclic AMP levels. Here we studied the alterations in the stimulatory action of cholera toxin and other agents on the adenylyl cyclase system, as well as the status of Gs and Gi protein subunits during the liver proliferation that follows bile duct ligation in rats. The stimulatory effects of glucagon and vasoactive intestinal peptide (which act through membrane receptors) or guanosine 5'-[beta gamma-imido]triphosphate (which interacts with G proteins) and forskolin (which directly activates the adenylyl cyclase catalytic subunit) on liver adenylyl cyclase activity were blunted in cholestasis. The results indicated an impairment in the stimulatory interaction between the alpha s subunit of Gs protein and the adenylyl cyclase catalytic subunit. Indeed, we observed an important decrease in the stimulation of adenylyl cyclase activity by cholera toxin in cholestasis that was accompanied by a reduced extent of [32P]ADP ribosylation of alpha s protein catalyzed by cholera toxin, as revealed by the poor labeling of the 42,000 Da band in liver membranes from cholestatic rats. However, there was no change in the amount of alpha s or beta proteins as measured with immunoblotting techniques. Experiments on [32P]ADP ribosylation of alpha i subunits of Gi proteins indicated an impairment in liver membranes from cholestatic rats, whereas Western blotting for the detection of alpha i subunits showed decreased alpha i3 and increased alpha i2 levels in this condition. Further efforts are needed to better understand the molecular mechanisms underlying the relationship between the observed divergent expression of Gs and Gi proteins and liver cell proliferation in the cholestatic liver.

VIP receptor/effector system in liver membranes from cholestatic rats

A reduced efficacy of VIP (43% of the control) without modification in its potency (ED50 = 2.2 nM) was observed in regenerating rat liver after cholestasis (bile duct ligation). The same occurred with glucagon-stimulated adenylyl cyclase activity because the efficacy of this VIP-related peptide was also reduced (53% of the control) without changes in its potency in this experimental model. The equilibrium binding data revealed no changes in either the affinity or the VIP binding capacity of liver membranes during cholestasis. Cross-linking experiments gave the same apparent molecular mass for the liver VIP-receptor complex (52 kDa) in control and cholestatic rats. The coupling between the VIP receptor and the Gs-protein was also unaffected because the sensitivity of VIP binding to GTP did not change after bile duct ligation. However, liver membranes from cholestatic rats showed a low extent of both ADP-ribosylation of the Gs-protein alpha subunit (as assessed with cholera toxin) and adenylyl cyclase stimulation by a direct effector such as forskolin. Thus, VIP-stimulated adenylyl cyclase activity is decreased in regenerating liver after cholestasis due probably to an impairment in the interaction between Gs-protein and adenylyl cyclase as well as a defect in the enzyme itself.

Experimentally induced colon cancer metastases in rat liver increase the proliferation rate and capacity for purine catabolism in liver cells

Metastases in rat liver were generated experimentally by intraportal injection of colon cancer cells to investigate the effects of cancerous growth on the metabolism of surrounding liver tissue. Maximum activities (capacity) of glucose-6-phosphate dehydrogenase, phosphogluconate dehydrogenase, lactate dehydrogenase, succinate dehydrogenase, alkaline phosphatase, 5'-nucleotidase, xanthine oxidoreductase, purine nucleoside phosphorylase and adenosine triphosphatase have been determined. Two types of metastases were found, a small type surrounded by stroma and a larger type in direct contact with hepatocytes. Both types affected the adjacent tissue in a similar way suggesting that the interactions were not mediated by stroma. High capacity of the degradation pathway of extracellular purines released from dead cells of either tumours or host tissue was found in stroma and sinusoidal cells. Metastases induced both an increase in the number of Kupffer cells and proliferation of hepatocytes. The distribution pattern in the liver lobulus of most enzymes investigated did not change distinctly. However, activity of alkaline phosphatase, succinate dehydrogenase and phosphogluconate dehydrogenase was increased in hepatocytes directly surrounding metastases. These data imply that the overall metabolic zonation in liver lobuli is not dramatically disturbed by the presence of cancer cells despite the fact that various metabolic processes in liver cells are affected.

Reversibility of cholestatic changes following experimental common bile duct obstruction: fact or fantasy?

In 36 male Wistar rats extrahepatic cholestasis was induced by ligation and transsection of the common bile duct. After 1, 2 and 3 weeks of cholestasis the bile flow was restored by means of a Roux-en-Y choledochojejunostomy. Plasma levels of bilirubin, alkaline phosphatase, GOT and clotting factor X were measured weekly. Liver biopsies were taken at the time of restored bile flow as well as 3 and 8 weeks thereafter. Histochemical reaction for lactate dehydrogenase activity and Sirius Red F3BA staining were used as measure for functional liver parenchyma and collagen, respectively. Acid phosphatase, alkaline phosphatase and 5'-nucleotidase activities as well as the glycogen content were demonstrated in cryostat sections of the same biopsies. After 1, 2 and 3 weeks of common bile duct obstruction, levels of bilirubin, alkaline phosphatase and GOT significantly increased, whereas levels of clotting factor X decreased. RBF resulted in normalization of all these levels to control range. The volume density of functional parenchyma was found to be reduced to 90%, 73% and 64% of the control values following 1, 2 and 3 weeks of common bile duct obstruction respectively, returning to 96%, 94% and 88% at 8 weeks, respectively, after restored bile flow. The collagen content increased significantly during cholestasis up to 5-fold after 3 weeks of common bile duct obstruction. After restored bile flow, a slight decrease of collagen was measured in some animals but in none of the three groups a return to normal values appeared. Cholestasis induced an alteration in localization and/or activity of the three enzymes analyzed as well as a depletion of glycogen stores. All changes in activity and distribution pattern of the three enzymes, as well as the glycogen depletion during common bile duct obstruction normalised after restored bile flow was performed. However, the longer common bile duct obstruction had existed, the longer period was needed for full recovery. In conclusion, even after 3 weeks of common bile duct obstruction the parenchyma/stroma relationship grossly normalized after restored bile flow with an almost complete restoration of the parenchyma and a concomitant recovery of liver function. However, collagen once formed, did not disappear but remained as more condensed septa, which apparently did not interfere with normal function.

Metabolic zonation of the liver: regulation and implications for liver function

Liver parenchyma shows a remarkable heterogeneity of the hepatocytes along the porto-central axis with respect to ultrastructure and enzyme activities resulting in different cellular functions within different zones of the liver lobuli. According to the concept of metabolic zonation, the spatial organization of the various metabolic pathways and functions forms the basis for the efficient adaptation of liver metabolism to the different nutritional requirements of the whole organism in different metabolic states. The present review summarizes current knowledge about this heterogeneity, its development and determination, as well as about its significance for the understanding of all aspects of liver function and pathology, especially of intermediary metabolism, biotransformation of drugs and zonal toxicity of hepatotoxins.

Assessment of lysosomal function by quantitative histochemical and cytochemical methods

Quantitative histochemistry and cytochemistry enables a direct link to be made between metabolic functions such as the activity of lysosomal enzymes and the morphology of a tissue or a type of cell. Several approaches exist such as microchemistry based on (bio)chemical analysis of a single cell or a small piece of tissue dissected from a freeze-dried section. This technique has been routinely used for prenatal diagnosis of inherited enzyme defects and especially of lysosomal storage diseases. Other approaches are cytofluorometry or cytophotometry, which are based on the principle that a fluorescent or coloured final reaction product is precipitated at the site of the enzyme. The amount of final reaction product is analysed per cell or per unit volume of tissue using either a microscope cytofluorometer or flow cytometer for fluorescence measurements or an image analysing system or scanning and integrating cytophotometer for absorbance measurements. In principle, fluorescence methods are to be preferred over chromogenic methods because they are more sensitive and enable multiparameter analysis. However, only a limited number of fluorogenic methods are at hand that give a final reaction product which is sufficiently water-insoluble to guarantee good localisation. The best results have been obtained with methods based on naphthol AS-TR derivatives and with methods for the demonstration of protease activity using methoxynaphthylamine derivatives as substrates and 5'-nitrosalicylaldehyde as coupling reagent. Chromogenic methods are far better with respect to localisation properties and, therefore, most commonly used for quantitative histochemical analysis of lysosomal enzyme activities.(ABSTRACT TRUNCATED AT 250 WORDS)