Search PubMed⌕ Search

Biomedical subjects

P Bannasch

Publications and source records attributed to P Bannasch.

At least 37 records · Page 2Linked to original sources
PubMed1998

Cytokeratin expression is reduced in glycogenotic clear hepatocytes but increased in ground-glass cells in chronic human and woodchuck hepadnaviral infection.

Hepatocytes of normal adult liver express cytokeratins (CKs) 8/18, but bile duct cells additionally contain CK7/19. We have previously demonstrated the frequent occurrence of foci of altered hepatocytes in association with hepatic tumors in humans and provided evidence for a preneoplastic nature of the focal lesions. In this study, we investigated the CK expression in both the preneoplastic lesions and extrafocal parenchyma. Sixty-seven explanted livers with cirrhosis or advanced fibrosis harboring preneoplastic focal lesions, with or without hepatitis B virus (HBV) infection, as well as 9 livers with HBV-associated fulminant hepatitis, were studied for the expression of CK7/8/14/18/19. Five livers from woodchucks infected with the woodchuck hepatitis virus (WHV) were also investigated. Glycogenotic clear hepatocytes were negative or weakly positive for CK8/18, while amphophilic hepatocytes were strongly positive for these CKs, the changes being associated with marked reduction and increase, respectively, of highly organized membranous components in their cytoplasm. This allows the distinct recognition of the clear-cell and clear-cell-dominant preneoplastic lesions in the human and woodchuck livers. In ground-glass hepatocytes expressing viral antigens, an unusual accumulation of CK8/18 was observed, but there was no evidence of preferential necrosis of ground-glass hepatocytes. Many CK7- and CK19-positive ductular (oval) cells were found in extrafocal liver tissue, but only rarely were they present within focal lesions.

Adult↗
PubMed1998

A new method for flat-embedding large native cryostat sections for targeting small preneoplastic lesions in comparative ultrastructural and ultracytochemical investigations.

Ultrastructural studies of rare and small cellular lesions in pathologically altered tissue are difficult to perform by applying conventional electron microscopic preparation. The search for lesions, often consisting of only a few cells in randomly obtained small specimen blocks, is time consuming and often without success. The methodological requirements for comparative enzyme cytochemical and morphological studies, i.e., preservation of both enzyme activity and ultrastructure, are divergent. By processing large native cryostat sections for electron microscopy, small preneoplastic focal lesions were successfully targeted in liver and kidney. Glucose-6-phosphatase, alkaline phosphatase, acid phosphatase, catalase, and cytochrome c oxidase activities were distinctly localized to endoplasmic reticulum, canalicular membrane, lysosomes, peroxisomes, and mitochondria, respectively, in the morphologically altered cells. Fixation of serial cryostat sections and enzyme reactions were both carried out through a semipermeable membrane except those for cytochrome c oxidase, which was demonstrated after fixation through the membrane by floating the section in incubation medium containing cytochrome c. Thereafter, the sections were flat embedded and polymerized between epoxy resin disks and aluminum dishes fitting exactly together. The objects of interest were identified in the light microscope, cut out, and reembedded in reversed gelatine capsules. By using this technique an ultrastructural preservation was achieved similar to that seen after immersion fixation. The enzyme activities were clearly localized without diffusion of the reaction product or unspecific deposits. The procedure permits precise targeting and complex studies of rare and small lesions, and opens new perspectives for the use of cryo-preserved tissue.

Animals↗
PubMed1998

A model for hepatocarcinogenesis treating phenotypical changes in focal hepatocellular lesions as epigenetic events.

The major paradigm for mathematically describing the carcinogenic process has been through the use of multistage models. Multistage models are made up of numerous compartments representing cells in various stages on the way to malignancy and where movement from one cell class to another is assumed to have exponential waiting time. Once a cell is in a particular class, clonal expansion through a linear birth-death process increases the size of the compartment. These models are characterized by movement of single cells from one compartment to another rather than clonal colonies of cells. However, there is some evidence to suggest that, in certain organs for certain types of agents, preneoplastic lesions with different phenotypes arise directly from an entire clonal colony rather than from a single cell within that colony. This manuscript describes a simple mathematical model of carcinogenesis using both persistent changes of single or several cells (to start the process) and shifting of colonies to describe the stages of the model. Likelihoods for the use of the model with data on colonies of preneoplastic lesions are described and applied to real data.

Animals↗
PubMed1998

Pyruvate kinase isoenzyme shift from L-type to M2-type is a late event in hepatocarcinogenesis induced in rats by a choline-deficient/DL-ethionine-supplemented diet.

Rats received a choline-deficient diet containing 0.1% (w/w) DL-ethionine (CDE) for 4, 10, 14 or 22 weeks. A separate group was treated for 4 weeks with CDE and then received a normal diet for 4 weeks. The L and M2 isoenzymes of pyruvate kinase were immunocytochemically demonstrated in liver sections. L-PK expression was strongly reduced in the hepatocytes after 4 weeks of treatment and remained low until the end of the study. Withdrawal of CDE after 4 weeks followed by 4 weeks normal diet resulted in a nearly full recovery of L-PK expression as compared to untreated controls. At later stages (10-22 weeks of CDE- treatment) many pseudolobules, preneoplastic foci of altered hepatocytes (FAH) such as combined clear/acidophilic cell foci (CCF/ACF) and mixed/basophilic cell foci (MCF/BCF), and hepatocellular adenomas (HCA) were observed. Pseudolobules showed a slight reduction in L-PK-expression, and were negative for M2-PK. In all clear cell components of CCF/ACF excessively storing glycogen, L-PK-expression was increased compared to both the surrounding parenchyma and hepatocytes of controls. In acidophilic cell components with less pronounced glycogen storage L-PK expression was similar to that of pseudolobules showing a slightly reduced content of this enzyme protein. M2-PK was invariably negative in CCF/ACF. In most MCF glycogen-storing subpopulations expressed L-PK, whereas in all glycogen-poor basophilic populations L-PK protein was strongly reduced. M2-PK was not expressed in most of these MCF. However, in rare MCF the reduction in L-PK expression was combined with a significant expression of M2-PK. In HCA M2-PK underwent a further increase, although to a variable degree, while L-PK remained strongly reduced. Our results show that an isoenzyme shift from L-PK to M2-PK takes place at a late stage of the hepatocarcinogenic process, and that those MCF with a low L-PK expression and a reexpression of M2-PK most probably represent the direct precursor lesions of hepatocellular neoplasms.

Animals↗
PubMed1998

Xenomorphic hepatocellular precursors and neoplastic progression of tigroid cell foci induced in rats with low doses of N-nitrosomorpholine.

Tigroid cell foci (TCF) are a well-defined entity induced in rat liver by chemical carcinogens, their significance for hepatocarcinogenesis being controversial. Using cytomorphological, cytochemical and morphometric approaches, we studied the evolution and fate of TCF sequentially from 7 to 110 weeks in groups of 50 male Sprague-Dawley rats, which remained untreated or received N-nitrosomorpholine (NNM) orally at concentrations of 3 and 1 mg/kg body wt/day for 7 and up to 75 weeks, respectively. An increased incidence of hepatocellular neoplasms developed in exposed animals compared with controls, which was significant for adenomas at both dose levels, and for carcinomas (HCC) after the longer exposure to the lower dose level (P < 0.0001). TCF appeared frequently in addition to other types of proliferative foci of altered hepatocytes (FAH) including clear/acidophilic and mixed cell foci (MCF) in NNM-treated and rarely in untreated rats. Striking similarities in the cellular phenotypes of TCF and many hepatocellular neoplasms indicated the potential of TCF for progression to both adenomas and carcinomas. TCF emerged from xenomorphic cell foci (XCF), which consisted of hypertrophied hepatocytes typically presenting an enlarged nucleus, abundant glycogen, smooth and rough endoplasmic reticulum, altered activities of several enzymes of carbohydrate metabolism and an increased cell proliferation (P < 0.001) compared with the extrafocal parenchyma. TCF shared many features with XCF, but their basophilia and proliferative activity was higher. The number of FAH appearing at the two dose levels of NNM was similar but the average size of TCF and MCF was frequently higher at late time points in the group developing a significantly higher incidence of HCC, which suggests a pronounced acceleration of neoplastic conversion in established preneoplastic cell populations rather than the induction of additional FAH by sustained effects of low doses of carcinogens.

Animals↗
PubMed1998

Overexpression of insulin receptor substrate-1 emerges early in hepatocarcinogenesis and elicits preneoplastic hepatic glycogenosis.

Insulin receptor substrate-1 (IRS-1) is a multisite docking protein occupying a central position in signaling cascades stimulated by a number of growth factors including insulin. Using Western blotting and immunohistochemistry, we investigated the expression of IRS-1 in more than 400 preneoplastic foci of altered hepatocytes and in 12 hepatocellular carcinomas induced in rats by oral administration of N-nitrosomorpholine. In both N-nitrosomorpholine-treated and untreated rat livers, IRS-1 was demonstrable by Western blotting, but with the exception of a few single hepatocytes it was not detectable in the normal parenchyma by immunohistochemistry. In contrast, immunohistochemistry revealed that IRS-1 was strongly expressed in the majority of foci of altered hepatocytes particularly in approximately 97% of the clear/acidophilic and mixed cell foci showing excessive storage of glycogen (glycogenosis). In glycogen-poor basophilic foci of altered hepatocytes and hepatocellular carcinomas, IRS-1 was not detected by immunohistochemistry, but a weak expression was observed in small subpopulations of three hepatocellular carcinomas containing remnants of glycogen. These results indicate that the focal overexpression of IRS-1 is an early event in hepatocarcinogenesis, which is closely correlated with preneoplastic hepatic glycogenosis. During progression from glycogenotic foci to hepatocellular carcinomas, IRS-1-overexpression is gradually down-regulated, and this late event is associated with a fundamental metabolic shift leading to the malignant neoplastic phenotype.

Animals↗
PubMed1997

Enhancement and phenotypic modulation of N-nitrosomorpholine-induced hepatocarcinogenesis by dehydroepiandrosterone.

Hepatocarcinogenesis was induced in male and female rats by continuous administration of the adrenal steroid dehydroepiandrosterone (DHEA; 0.6% in the diet) with and without previous treatment with N-nitrosomorpholine (NNM; 120 mg/l drinking water for 7 weeks). DHEA treatment alone resulted in hepatocellular adenomas (HCA) and carcinomas (HCC) after 72-84 weeks, the incidence of both benign and malignant neoplasms being higher in females than in males. After DHEA administration for up to 32 weeks subsequent to NNM, the incidence of HCA and HCC was significantly higher (HCA, 42%; HCC, 42%) than after NNM alone (HCA, 33%; HCC, 28%). While total tumor incidence was similar in male (63%) and female (60%) rats after NNM treatment alone, it was higher in females (87%) than in males (80%) after NNM/DHEA treatment. The difference between the genders was mainly due to the higher incidence of HCC in females. Morphometric analysis of preneoplastic foci of altered hepatocytes (FAH) yielded that DHEA treatment did not increase the average total number of FAH induced by NNM, but caused a modulation of the phenotype of FAH from the glycogenotic/basophilic to the amphophilic cell lineage. The results confirm that DHEA acts as a hepatocarcinogen and show for the first time that it enhances NNM-induced hepatocarcinogenesis in rats.

Adenoma, Liver Cell↗
PubMed1997

Metabolic activation of aflatoxin B1 to aflatoxin B1-8,9-epoxide in woodchucks undergoing chronic active hepatitis.

Chronic hepatitis B virus infection as well as consumption of food contaminated with the mycotoxin aflatoxin B1 are considered to be 2 major risk factors for the development of primary liver cancer in humans. Furthermore, epidemiological surveys indicate that hepatitis B virus and aflatoxin B1 might act synergistically to induce primary liver cancer. In the present study, we have tested the hypothesis that the metabolic activation of aflatoxin B1 to aflatoxin B1-8,9-epoxide, the ultimate mutagenic and carcinogenic mycotoxin metabolite, is enhanced in an experimental model of chronic hepatitis using woodchucks, chronically infected with the woodchuck hepatitis virus. Woodchuck liver microsomes were incubated with radiolabeled aflatoxin B1, the resulting aflatoxin B1-8,9-epoxide was trapped as a glutathione conjugate and its formation rate was determined by a reversed-phase HPLC analysis. In woodchuck hepatitis virus-positive woodchucks, activation of aflatoxin B1 to aflatoxin B1-8,9-epoxide was reduced when compared to woodchuck hepatitis virus-free animals, and the extent of the reduction was dependent on the severity of the hepatitis. Hence, at least in woodchucks, a chronic hepadnaviral infection does not lead to an enhanced activation of aflatoxin B1.

Aflatoxin B1↗
PubMed1997

Establishment and characterization of a nontumorigenic cell line derived from a human hepatocellular adenoma expressing hepatocyte-specific markers.

In the present study the establishment and characterization of a nontumorigenic liver epithelial cell line (HACL-1) derived from a human hepatocellular adenoma is described. The HACL-1 cells have a finite life span (i.e., they proliferate for a period of 2 months and then senesce), show cell-cell contact inhibition, do not grow in soft agar, are not tumorigenic when injected in nude mice, and possess a normal diploid karyotype. The cultured cells resemble hepatocytes, but exhibit some features of dedifferentiation. At the ultrastructural level the cells are endowed with round or oval nuclei, abundant cytoplasmic organelles, and varying amounts of glycogen. The rough endoplasmic reticulum is disorganized, while peroxisomes and matrix granules within mitochondria are lacking. HACL-1 cells are cytokeratin 18-positive as well as (transiently) albumin- and alpha-fetoprotein-positive, but do not express cytokeratin 19. Furthermore, no mutations were observed in exons 5-8 of the tumor suppressor gene p53. Taken together these results show that HACL-1 cells are nontumorigenic proliferating liver epithelial cells, which might prove to be of great value in future studies on diverse aspects of human liver cell biology and carcinogenesis.

Adenoma, Liver Cell↗
PubMed1997

Human hepatic preneoplasia: phenotypes and proliferation kinetics of foci and nodules of altered hepatocytes and their relationship to liver cell dysplasia.

Foci of altered hepatocytes (FAH) represent preneoplastic lesions, as shown in various animal models of hepatocarcinogenesis, but their significance in the human liver has not been established. The cellular composition, size distribution and proliferation kinetics of FAH in 163 explanted and resected human livers with or without hepatocellular carcinoma (HCC) and their possible association with small-cell change of hepatocytes (SCC) were therefore studied. FAH, including glycogen-storing foci, were found in 84 of 111 cirrhotic livers, demonstrating higher incidences in cases with (29/32) than in those without HCC (55/79). FAH were observed more frequently in HCC-free cirrhosis associated with hepatitis B or C virus or chronic alcoholic abuse (high-risk group) (37/47) than in that due to other causes (low-risk group) (12/21). MCF, predominant in cirrhotic livers of the high-risk group, were more proliferative, larger and more often involved in formation of nodules of altered hepatocytes (39.3%) than were GSF (8.5%). The results suggest that the FAH are preneoplastic lesions, MCF being more advanced than GSF. Oncocytic and amphophilic cell foci were also observed, but their significance remains to be clarified. Two types of SCC, namely diffuse and intrafocal SCC, were identified, but only intrafocal SCC was found to be related to increased proliferative activity and more frequent nodular transformation of the FAH involved, suggesting a close association with progression from FAH to HCC.

Adolescent↗
PubMed1997

Early bioenergetic changes in hepatocarcinogenesis: preneoplastic phenotypes mimic responses to insulin and thyroid hormone.

Biochemical and molecular biological approaches in situ have provided compelling evidence for early bioenergetic changes in hepatocarcinogenesis. Hepatocellular neoplasms regularly develop from preneoplastic foci of altered hepatocytes, irrespective of whether they are caused by chemicals, radiation, viruses, or transgenic oncogenes. Two striking early metabolic aberrations were discovered: (1) a focal excessive storage of glycogen (glycogenosis) leading via various intermediate stages to neoplasms, the malignant phenotype of which is poor in glycogen but rich in ribosomes (basophilic), and (2) an accumulation of mitochondria in so-called oncocytes and amphophilic cells, giving rise to well-differentiated neoplasms. The metabolic pattern of human and experimentally induced focal hepatic glycogenosis mimics the phenotype of hepatocytes exposed to insulin. The conversion of the highly differentiated glycogenotic hepatocytes to the poorly differentiated cancer cells is usually associated with a reduction in gluconeogenesis, an activation of the pentose phosphate pathway and glycolysis, and an ever increasing cell proliferation. The metabolic pattern of preneoplastic amphophilic cell populations has only been studied to a limited extent. The few available data suggest that thyromimetic effects of peroxisomal proliferators and hepadnaviral infection may be responsible for the emergence of the amphophilic cell lineage of hepatocarcinogenesis. The actions of both insulin and thyroid hormone are mediated by intracellular signal transduction. It is, thus, conceivable that the early changes in energy metabolism during hepatocarcinogenesis are the consequence of alterations in the complex network of signal transduction pathways, which may be caused by genetic as well as epigenetic primary lesions, and elicit adaptive metabolic changes eventually resulting in the malignant neoplastic phenotype.

Animals↗
PubMed1997

Hepatic zonation of the induction of cytochrome P450 IVA, peroxisomal lipid beta-oxidation enzymes and peroxisome proliferation in rats treated with dehydroepiandrosterone (DHEA). Evidence of distinct zonal and sex-specific differences.

Dehydroepiandrosterone (DHEA) is an intermediate product in the synthesis of male and female sex hormones in the adrenal cortex of man. In livers of rats and mice DHEA increases the levels of cytochrome P450 IVA and peroxisomal beta-oxidation enzymes associated with peroxisome proliferation. Prolonged treatment of rats with DHEA induces liver tumors that are more frequent in females arising mainly in the periportal regions of the liver lobule (Metzger et al., Toxicol. Pathol. 23, 591-605, 1995). Because of paucity of information on hepatic zonation of peroxisomal response to DHEA and controversial reports on gender-specific differences of its effects the present study was undertaken using qualitative immunohistochemical and quantitative immunoelectron microscopical techniques in addition to Western blotting. Rats were treated for 24 weeks with 0.6% DHEA supplied with diet. Immunoblot analysis revealed marked induction of peroxisomal beta-oxidation enzymes, which by quantitative analysis was equally strong in male and female animals, whilst catalase and urate-oxidase were not increased. Cytochrome P450 IVA, in contrast, was induced significantly stronger in male than in female rats. Immunohistochemistry confirmed the induction of cytochrome P450 IVA showing a marked lobular gradient in female animals with strong induction in pericentral and almost no induction in periportal regions of the liver lobule. In male animals cytochrome P450 IVA was expressed more uniformly across the liver lobule. A similar sex specific zone-dependent response was observed for peroxisomes. DHEA induced in females a significant zonal gradient with marked peroxisome proliferation and a strong induction of peroxisomal hydratase/dehydrogenase in pericentral hepatocytes and a much smaller response in periportal regions. Livers of male animals, in contrast, showed a uniform peroxisomal proliferation to DHEA with only slight zonal differences. The striking homologies of the induction patterns of cytochrome P450 IVA and the peroxisome proliferation in both sexes support the notion of a functional relationship. In view of the almost exclusive periportal localization of DHEA-induced tumors in female rats in contrast to the pericentral localization of the peroxisomal proliferation shown by this study, it seems likely that other factors in addition to peroxisome proliferation may contribute to the hepatocarcinogenic effect of DHEA.

Acyl-CoA Oxidase↗
PubMed1997

Hepatocellular neoplasms induced by low-number pancreatic islet transplants in streptozotocin diabetic rats.

We have previously demonstrated in short-term experiments that altered hepatocytes in liver acini draining the blood from intraportally transplanted pancreatic islets in streptozotocin-induced diabetic rats with mild persisting diabetes resemble those in preneoplastic foci of altered hepatocytes. We now present the results of long-term studies (up to 22 months) in this animal model. Glycogen-storing foci (which were the first parenchymal alteration observed some days after transplantation) persisted at least for 6 months, when the first mixed-cell foci and the first hepatocellular adenoma emerged. After 15 to 22 months, 86% of the animals exhibited at least one hepatocellular adenoma and four animals (19%) showed a hepatocellular carcinoma. The transplants were found in a close spatial relationship with the preneoplastic foci and the hepatocellular neoplasms. The mitotic indices, the 5-bromo-2'-desoxyuridine labeling indices and the apoptotic indices showed significant differences between the unaltered liver parenchyma, different types of preneoplastic foci, and hepatocellular neoplasms. The immunohistochemical expression of transforming growth factor-alpha increased during the stepwise development from glycogen-storing liver acini to hepatocellular carcinomas. Hepatocarcinogenesis in this new animal model is probably due to the hormonal and growth-stimulating effects of insulin secreted by the intraportally transplanted islets of Langerhans in diabetic rats.

Adenoma↗
PubMed1996

Increase of lipid peroxidation in rat liver microsomes by dehydroepiandrosterone feeding.

Oral administration of the adrenal steroid dehydroepiandrosterone (DHEA), a peroxisome proliferator and hepatocarcinogen in the rat, caused an increase in NADPH-dependent lipid peroxidation in microsomes isolated from rat liver and kidney cortex, but not from brain. The increase of liver microsomal lipid peroxidation was greater in male than in female rats. the effect of DHEA on lipid peroxidation became discernible after feeding steroid-containing diet (0.6%) to male and female rats for 2 and 3 days and reached maximal levels at 1 and 2 weeks, respectively. The increase of microsomal lipid peroxidation reached a plateau stimulation at 0.05% in the diet. The addition of DHEA in the concentration range 0.1-100 microM to microsomes isolated from control rats had no effect on lipid peroxidation. Furthermore, a significant increase of the endogenous concentration of thiobarbituric acid reactive substances was found in microsomes after DHEA-administration at 0.05% in the diet. These results provide in vivo evidence that DHEA can cause lipid peroxidation in rat liver. Administration of DHEA at 0.6% in the diet for 7 consecutive days also significantly enhanced NADH- and ascorbate-dependent lipid peroxidation in liver microsomes. The DHEA-stimulated rat liver microsomal lipid peroxidation was completely inhibited by EDTA but not by superoxide dismutase, catalase or mannitol applied as OH-radical scavenger. The findings indicate that membrane lipid peroxidation is an early effect of DHEA, and that this process may be involved in the steroid-induced carcinogenesis in rats.

Adenosine Diphosphate↗
PubMed1996

Changes in catalase and glucose-6-phosphatase distribution patterns within oval cell compartment as possible differentiation markers during viral hepatocarcinogenesis in woodchucks.

Cytochemical analysis at the ultrastructural level was performed to characterize expression of catalase and glucose-6-phosphatase (G6Pase) activity as possible differentiation markers in oval cells proliferating during hepatocarcinogenesis induced in woodchucks by chronic infection with the woodchuck hepatitis virus (WHV) and additional treatment with aflatoxin B1 (AFB1). Oval cells from WHV-carriers treated with AFB1 showed two types of catalase-positive organelles: 1) microperoxisomes appearing as small strongly osmiophilic bodies corresponding to those present in biliary cells from control woodchucks, 2) peroxisomes with a hepatic staining pattern resembling those of mature hepatocytes but lacking a nucleoid. While in oval cells penetrating into the parenchyma a catalase-positive reaction product was restricted to rare microperoxisomes, in close vicinity to the portal tract about 30% of the oval cells produced peroxisomes with a hepatic staining pattern, indicating the existence of two different populations within the oval cell compartment. Peroxisomes with a hepatic staining pattern formed clusters and exhibited pleomorphism with marked variation in shape and size, the size sometimes coming up to that of normal hepatocellular peroxisomes. Serial sections revealed the complex organization of these peroxisomes. They consisted of several interconnected segments forming a peroxisomal reticulum. These findings are consistent with the hypothesis that a subpopulation of oval cells represents committed precursor cells capable of differentiating into hepatocytes. Activity of G6Pase was not demonstrable in this subpopulation of oval cells and became positive only in transitional cells. Differential expression of catalase and G6Pase activity in a stepwise fashion within the oval cell compartment appear to mark differentiation of oval cells into hepatocytes. Thus, elevated expression of catalase may be a useful early marker for the distinction of different subpopulations of oval cells committed to hepatic cell lineages before definitely changing their phenotype, whereas expression of G6Pase activity seems to begin later, accompanying morphological changes towards the phenotype of mature hepatocytes.

Animals↗
PubMed1996

Altered liver acini induced in diabetic rats by portal vein islet isografts resemble preneoplastic hepatic foci in their enzymic pattern.

As demonstrated previously, liver acini draining the blood from intraportally transplanted pancreatic islets in streptozotocin-diabetic rats are altered in various respects. The hepatocytes in these acini store glycogen and/or fat, and they show an increase in proliferation as well as in apoptotic activity. Thus, they are phenotypically similar to carcinogen-induced preneoplastic liver foci (glycogen-storing foci and sometimes also mixed cell foci). By means of catalytic enzyme histochemistry or immunohistochemistry, we investigated the activity of key enzymes of alternative pathways of carbohydrate metabolism and some additional marker enzymes (well known from studies on preneoplastic hepatic foci) in the altered liver acini surrounding the islet isografts. In addition, the expression of glucose transporter proteins 1 and 2 (GLUT-1 and GLUT-2) were investigated immunohistochemically. The activities of hexokinase, pyruvate kinase, glyceraldehyde-3-phosphate dehydrogenase, and glucose-6-phosphate dehydrogenase were increased, whereas the activities of glycogen phosphorylase, adenylate cyclase, glucose-6-phosphatase, and membrane-bound adenosine triphosphatase were decreased in the altered liver acini. The expression of GLUT-2 was also decreased. GLUT-1 and glutathione S-transferase placental form were not expressed, and the activities of glycogen synthase and gamma-glutamyl-transferase remained unchanged. All changes of the enzyme activities were in line with the well known effects of insulin and resembled alterations characteristic of preneoplastic liver foci observed in different models of hepatocarcinogenesis. It remains to be clarified in long-term experiments whether or not these foci represent preneoplastic lesions and may proceed to neoplasia.

Animals↗