Long-term cell culture of adult rat liver epithelial cells

Murine deficiency of peroxisomal L-bifunctional protein (EHHADH) causes medium-chain 3-hydroxydicarboxylic aciduria and perturbs hepatic cholesterol homeostasis

Peroxisomes play an essential role in the β-oxidation of dicarboxylic acids (DCAs), which are metabolites formed upon ω-oxidation of fatty acids. Genetic evidence linking transporters and enzymes to specific DCA β-oxidation steps is generally lacking. Moreover, the physiological functions of DCA metabolism remain largely unknown. In this study, we aimed to characterize the DCA β-oxidation pathway in human cells, and to evaluate the biological role of DCA metabolism using mice deficient in the peroxisomal L-bifunctional protein (Ehhadh KO mice). In vitro experiments using HEK-293 KO cell lines demonstrate that ABCD3 and ACOX1 are essential in DCA β-oxidation, whereas both the bifunctional proteins (EHHADH and HSD17B4) and the thiolases (ACAA1 and SCPx) have overlapping functions and their contribution may depend on expression level. We also show that medium-chain 3-hydroxydicarboxylic aciduria is a prominent feature of EHHADH deficiency in mice most notably upon inhibition of mitochondrial fatty acid oxidation. Using stable isotope tracing methodology, we confirmed that products of peroxisomal DCA β-oxidation can be transported to mitochondria for further metabolism. Finally, we show that, in liver, Ehhadh KO mice have increased mRNA and protein expression of cholesterol biosynthesis enzymes with decreased (in females) or similar (in males) rate of cholesterol synthesis. We conclude that EHHADH plays an essential role in the metabolism of medium-chain DCAs and postulate that peroxisomal DCA β-oxidation is a regulator of hepatic cholesterol biosynthesis.

The Last Half Century of Fish Explant and Organ Culture

Explants are three-dimensional tissue fragments maintained outside the organism. The goals of this article are to review the history of fish explant culture and discuss applications of this technique that may assist the modern zebrafish laboratory. Because most zebrafish workers do not have a background in tissue culture, the key variables of this method are deliberately explained in a general way. This is followed by a review of fish-specific explantation approaches, including presurgical husbandry, aseptic dissection technique, choice of media and additives, incubation conditions, viability assays, and imaging studies. Relevant articles since 1970 are organized in a table grouped by organ system. From these, I highlight several recent studies using explant culture to study physiological and embryological processes in teleosts, including circadian rhythms, hormonal regulation, and cardiac development.

Comparison of commercially available media for hepatic differentiation and hepatocyte maintenance

Human hepatocytes are essential materials in pharmaceutical researches. Not only primary human hepatocytes (PHH) but also human iPS cell-derived hepatocyte-like cells (human iPS-HLCs) are expected to be applied as materials for pharmaceutical researches. To date, several culture media have been developed for culturing human hepatocytes. However, there have been no reports comparing these media to determine which is most suitable for culturing human hepatocytes. In this study, we compared five commercial media (Hepatocyte Culture Medium (HCM), HepatoZYME-SFM, Cellartis Power Primary HEP Medium, DMEM/F12, and William’s E Medium (WEM)) to determine which is most suitable for culturing PHH and human iPS-HLCs. In hepatic differentiation of human iPS cells (day 14–25 of differentiation), albumin (ALB) and urea secretion abilities and CYP2C9, CYP2C19, and CYP3A4 activities were the highest when using HCM or WEM. During maintenance of human iPS-HLCs, ALB and urea producing abilities and CYP2C9, CYP2C19, and CYP3A4 activities were the highest when using HCM. Importantly, we found that human iPS-HLCs cultured in HCM were maintained for 3 weeks or more without impairment of their hepatic functions. These results suggest that it is necessary to select an optimal medium for hepatic differentiation and maintenance of human iPS-HLCs. In the case of PHH culture, there was little difference in hepatic functions among the five media. However, the CYP2C9, CYP2C19, and CYP3A4 activities were the highest when using HCM and WEM. In conclusion, it is important to select the optimal medium for specific application when carrying out pharmaceutical researches using human hepatocytes.

Human fetal liver cultures support multiple cell lineages that can engraft immunodeficient mice

During prenatal development the liver is composed of multiple cell types with unique properties compared to their adult counterparts. We aimed to establish multilineage cultures of human fetal liver cells that could maintain stem cell and progenitor populations found in the developing liver. An aim of this study was to test if maturation of fetal hepatocytes in short-term cultures supported by epidermal growth factor and oncostatin M can improve their ability to engraft immunodeficient mice. Fetal liver cultures supported a mixture of albumin⁺ cytokertin-19⁺ hepatoblasts, hepatocytes, cholangiocytes, CD14⁺⁺CD32⁺ liver sinusoidal endothelial cells (LSECs) and CD34⁺CD133⁺ haematopoietic stem cells. Transplantation of cultured cells into uPA-NOG or TK-NOG mice yielded long-term engraftment of hepatocytes, abundant LSEC engraftment and multilineage haematopoiesis. Haematopoietic engraftment included reconstitution of B-, T- and NK-lymphocytes. Colonies of polarized human hepatocytes were observed surrounded by human LSECs in contact with human CD45⁺ blood cells in the liver sinusoids. Thus, fetal liver cultures support multiple cell lineages including LSECs and haematopoietic stem cells while also promoting the ability of fetal hepatocytes to engraft adult mouse livers. Fetal liver cultures and liver-humanized mice created from these cultures can provide useful model systems to study liver development, function and disease.

Reassembly of Functional Human Stem/Progenitor Cells in 3D Culture

This chapter focuses on the culture of primary human cells from the salivary glands, typically parotid but also submandibular, where specialized acinar cells produce most of the components found in saliva and the intercalated ducts followed by striated ducts transport saliva to the oral cavity. Compared to many other epithelial cells, the zymogen-filled salivary acinar cells are very fragile, hence specialized techniques are needed to isolate and culture them. To reestablish the function of implantable 3D reassembled glands using tissue engineering approaches, it is critical to culture these cells in human-based matrices that permit them to move, reassemble, interconnect, and establish proper polarity by producing a basement membrane. Our team is working to develop a biologically based, implantable salivary gland replacement tissue for head and neck cancer patients suffering from post-radiation xerostomia using a "bottom up" reassembly paradigm. We use specialized extracellular matrix and growth factor supplemented hyaluronate hydrogels to promote reassembly of human salivary stem/progenitor cells (hS/PCs) isolated after surgical resection, a method we describe in this chapter. Cell-specific biomarkers are used to track the formation of the three major epithelial cell types comprising the salivary gland: acinar, ductal, and myoepithelial.

Culture Conditions Promoting Hepatocyte Proliferation and Cell Cycle Synchronization

The liver overcomes damages induced by harmful substances or viral infections and allows the use of extended resection in human therapy through its remarkable ability to regenerate. The regeneration process relies on the massive proliferation of differentiated hepatocytes that exit quiescence and undergo a limited number of cell cycles to restore the hepatic mass. Many discoveries on the regulation of hepatocyte proliferation have benefited from the use of in vitro models of cultures of primary hepatocytes as well as hepatoma cells as opposed to data obtained from in vivo models of liver regeneration, such as following partial hepatectomy in rodents. In this chapter, the most pertinent in vitro models used to promote the proliferation of hepatocytes and technical procedures to synchronize their progression throughout the cell cycle are presented with the goal to investigate the regulation of the hepatocyte cell cycle and the molecular pathways regulating liver regeneration.

Structure and expression of integrated hepatitis B virus genes in an HBs antigen producing human cell line (huGK-14)

A human continuous cell line (huGK-14) within a lineage of passaged cultures was investigated in the mode of integration and expression of hepatitis B virus (HBV) genes. HBV DNA was integrated in eight different sites of the cellular DNA, in each of which HBV genome was rearranged, fragmented, and/or partly deleted. Complete HBV genome that may lead to production of infectious virus particles was not detected in the cells nor in the culture medium. Clones of cDNA containing a complete coding frame for small HBs antigen protein (type adr) were obtained from mRNA of the cells. The cells were stable over the period of six months of cultivation and more than 60 population doublings in the mode of HBV integration and HBs mRNA expression.These results provide substantial evidence for the absence of an ability for the integrated DNA to create an infectious product in the cell; for the stable production of HBs mRNA from the cells, and suggest the usefulness of this cell line as a substrate for HBV vaccine production.

Establishing human lacrimal gland cultures with secretory function

Purpose

Dry eye syndrome is a multifactorial chronic disabling disease mainly caused by the functional disruptions in the lacrimal gland. The treatment involves palliation like ocular surface lubrication and rehydration. Cell therapy involving replacement of the gland is a promising alternative for providing long-term relief to patients. This study aimed to establish functionally competent lacrimal gland cultures in–vitro and explore the presence of stem cells in the native gland and the established in-vitro cultures.

Methods

Fresh human lacrimal gland from patients undergoing exenteration was harvested for cultures after IRB approval. The freshly isolated cells were evaluated by flow cytometry for expression of stem cell markers ABCG2, high ALDH1 levels and c-kit. Cultures were established on Matrigel, collagen and HAM and the cultured cells evaluated for the presence of stem cell markers and differentiating markers of epithelial (E-cadherin, EpCAM), mesenchymal (Vimentin, CD90) and myofibroblastic (α-SMA, S-100) origin by flow cytometry and immunocytochemistry. The conditioned media was tested for secretory proteins (scIgA, lactoferrin, lysozyme) post carbachol (100 µM) stimulation by ELISA.

Results

Native human lacrimal gland expressed ABCG2 (mean±SEM: 3.1±0.61%), high ALDH1 (3.8±1.26%) and c-kit (6.7±2.0%). Lacrimal gland cultures formed a monolayer, in order of preference on Matrigel, collagen and HAM within 15–20 days, containing a heterogeneous population of stem-like and differentiated cells. The epithelial cells formed ‘spherules’ with duct like connections, suggestive of ductal origin. The levels of scIgA (47.43 to 61.56 ng/ml), lysozyme (24.36 to 144.74 ng/ml) and lactoferrin (32.45 to 40.31 ng/ml) in the conditioned media were significantly higher than the negative controls (p<0.05 for all comparisons).

Conclusion

The study reports the novel finding of establishing functionally competent human lacrimal gland cultures in-vitro. It also provides preliminary data on the presence of stem cells and duct-like cells in the fresh and in-vitro cultured human lacrimal gland. These significant findings could pave way for cell therapy in future.

Enhanced growth and hepatic differentiation of fetal liver epithelial cells through combinational and temporal adjustment of soluble factors

Fetal liver epithelial cells (FLEC) are valuable for liver cell therapy and tissue engineering, but methods for culture and characterization of these cells are not well developed. This work explores the influence of multiple soluble factors on FLEC, with the long-term goal of developing an optimal culture system to generate functional liver tissue. Our comparative analysis suggests hepatocyte growth factor (HGF) is required throughout the culture period. In the presence of HGF, addition of oncostatin M (OSM) at culture initiation results in concurrent growth and maturation, while constant presence of protective agents like ascorbic acid enhances cell survival. Study observations led to the development of a culture medium that provided optimal growth and hepatic differentiation conditions. FLEC expansion was observed to be approximately twofold of that under standard conditions, albumin secretion rate was 2-3 times greater than maximal values obtained with other media, and the highest level of glycogen accumulation among all conditions was observed with the developed medium. Our findings serve to advance culture methods for liver progenitors in cell therapy and tissue engineering applications.

Lanford medium induces high quality hepatic lineage cell differentiation directly from mouse embryonic stem cell-derived mesendoderm

To establish an effective induction method for hepatic differentiation using serum-free media, the effects of activin in serum-containing and serum-free conditions on embryoid body (EB) induction into mesendoderm were investigated by Western blot analysis and real-time reverse transcription-polymerase chain reaction (RT-PCR) as a first step. The expression of P-smad2 and mesendodermal markers was markedly enhanced by 100ng/ml activin under serum-free conditions but were inhibited or masked under serum-containing conditions. Next, serum-free Lanford medium was used to attempt the direct induction of activin-treated EBs expressing mesendodermal markers into hepatic lineage cells and this induction was compared to that induced using Iscove's Modified Dulbecco's medium containing 20% fetal bovine serum. Once immersed in the Lanford medium, EBs began to show typical hepatic features by day 17, including Alb, AFP, TTR, and AAT expression detected by RT-PCR, and ALB, AFP, and CK18 expression detected by immunostaining. On day 22, these cells were of high quality characterized by the expression of metabolizing enzymes, including Ugt1a1, Slcola4, cyp3a11, cyp2b10, and cyp7a1 detected by real-time PCR, a 50-fold greater cyp3A11 response than control to 100muM dexamethasone stimulation, specific cellular uptake of indocyanine green, and glycogen storage in the cytoplasm. These results indicate that this simple two-step induction method under serum-free conditions induces hepatic lineage cells with high quality directly from mouse embryonic stem (ES) cell-derived mesendoderm.

Entry of duck hepatitis B virus into primary duck liver and kidney cells after discovery of a fusogenic region within the large surface protein

Hepatitis B viruses exhibit a narrow host range specificity that is believed to be mediated by a domain of the large surface protein, designated L. For duck hepatitis B virus, it has been shown that the pre-S domain of L binds to carboxypeptidase D, a cellular receptor present in many species on a wide variety of cell types. Nonetheless, only hepatocytes become infected. It has remained vague which viral features determine host range specificity and organotropicity. By using chymotrypsin to treat duck hepatitis B virus, we addressed the question of whether a putative fusogenic region within the amino-terminal end of the small surface protein may participate in viral entry and possibly constitute one of the determinants of the host range of the virus. Addition of the enzyme to virions resulted in increased infectivity. Remarkably, even remnants of enzyme-treated subviral particles proved to be inhibitory to infection. A noninfectious deletion mutant devoid of the binding region for carboxypeptidase D could be rendered infectious for primary duck hepatocytes by treatment with chymotrypsin. Although because of the protease treatment mutant and wild-type viruses may have become infectious in an unspecific and receptor-independent manner, their host range specificity was not affected, as shown by the inability of the virus to replicate in different hepatoma cell lines, as well as primary chicken hepatocytes. Instead, the organotropicity of the virus could be reduced, which was demonstrated by infection of primary duck kidney cells.

A serum-free Vero production platform for a chimeric virus vaccine candidate

MedImmune Vaccines has engineered a live, attenuated chimeric virus that could prevent infections caused by parainfluenza virus type 3 (PIV3) and respiratory syncytial virus (RSV), causative agents of acute respiratory diseases in infants and young children. The work here details the development of a serum-free Vero cell culture production platform for this virus vaccine candidate. Efforts to identify critical process parameters and optimize culture conditions increased infectious virus titers by approximately 2 log(10) TCID(50)/ml over the original serum-free process. In particular, the addition of a chemically defined lipid concentrate to the pre-infection medium along with the shift to a lower post-infection cultivation temperature increased virus titers by almost 100-fold. This improved serum-free process achieved comparable virus titers to the serum-supplemented process, and demonstrated consistent results upon scale-up: Vero cultures in roller bottles, spinner flasks and bioreactors reproducibly generated maximum infectious virus titers of 8 log(10) TCID(50)/ml.

Silybin reduces lipid peroxidation of rat hepatocyte membrane caused by cyclosporin A

An effect of cyclosporin A on lipid peroxidation in isolated rat hepatocytes was tested. A significant increase in lipid peroxidation marker (the concentration of lipofuscin-like pigments) was observed in samples incubated with cyclosporin A in comparison with the control. When hepatoprotective flavonoid silybin was added, the production of lipofuscin-like pigments decreased significantly. This result indicates a potential positive role of silybin in lowering of cyclosporin A side effects associated with the production of reactive oxygen species and plasma membrane damage.

Effect of culture conditions on the expression and function of Bsep, Mrp2, and Mdr1a/b in sandwich-cultured rat hepatocytes

Rat hepatocytes cultured in a sandwich configuration form functional canalicular networks. The influence of extracellular matrix configuration, medium composition, and confluency on the expression and function of Bsep, Mrp2, and Mdr1a/b in sandwich-cultured (SC) rat hepatocytes was examined. Primary rat hepatocytes were: (1) maintained in various extracellular matrix sandwich configurations, (2) cultured in Dulbecco's modified Eagle's medium (DMEM), Modified Chee's medium (MCM) or Williams' E medium (WME), and/or (3) plated at decreasing cell density. Bsep, Mrp2, and Mrdr1a/b expression in day 4 SC rat hepatocytes was assessed by Western blot; function was measured by accumulation of taurocholate, 5(and 6)-carboxy-2',7'-dichlorofluorescein, and rhodamine 123, respectively, in canalicular networks. In general, the extracellular matrix conditions examined resulted in similar protein expression and function. Function of Bsep, Mrp2, and Mdr1a/b was higher in SC rat hepatocytes maintained in DMEM or WME. Mrp2 and Mdr1a/b expression, representative of total cellular content, did not always correlate directly with function, which should be reflective of canalicular membrane expression. Mrp2 expression decreased significantly as cell density decreased in SC hepatocytes. Low plating density in Biocoat plates resulted in poor canalicular network formation and reduced function of Mrp2 and Mdr1a/b. Expression and/or function of Mrp2 and Mdr1a/b in rat hepatocytes cultured in a sandwich configuration may be influenced by plating density and media type.

TNFalpha-mediated extracellular matrix remodeling is required for multiple division cycles in rat hepatocytes

During liver regeneration, hepatocytes proliferate under the control of both proinflammatory cytokines such as tumor necrosis factor alpha (TNFalpha) and growth factors, in parallel to extracellular matrix remodeling. This study investigated mechanisms by which mitogen and extracellular matrix signals are linked for inducing proliferation of differentiated hepatocytes. The authors used adult rat hepatocytes in coculture with liver biliary cells, because cells are stably differentiated for several weeks, capable of extracellular matrix deposition, and unable to divide in response to growth factor alone. This work demonstrated that hepatocytes could undergo several proliferation waves without loss of differentiation by using alternating periods of TNFalpha/growth factor stimulation and deprivation. Three days after stimulation with TNFalpha and epidermal growth factor (EGF), up to 35% of hepatocytes divided. Demonstration was also provided that EGF alone only promoted cell progression up to late G(1), whereas TNFalpha was necessary for G(1)/S transition and Cdk1 induction. TNFalpha promoted an extracellular matrix (ECM) degradation that involved the matrix metalloproteinase MMP-9 induction through activation of NF-kappaB pathway. Finally, the authors showed that ECM remodeling signal was required for initiating any new hepatocyte division wave, in presence of mitogen. In conclusion, these results highlight that hepatocyte division is dependent on ECM deposition associated with differentiation status, and that ECM degradation signal is critical in controlling G(1)/S transition and Cdk1 induction. These results provide new insights for understanding the unique hepatocyte proliferation control and improving regeneration in patients suffering from liver damage.

Liver stem cells: a potential source of hepatocytes for the treatment of human liver disease

Severe liver injury often leads to the proliferation of oval cells, which differentiate along hepatocytic and biliary lineages. Because oval cells proliferate only when hepatocyte replication is impaired, they are considered to be the progeny of facultative liver stem cells (FLSCs). Identification and isolation of FLSCs has been hampered by the lack of markers that delineate these bipotential progenitors. We hypothesized that transition ductal cells are FLSCs because they are located in a unique anatomical niche sharing tight junctions with a neighboring hepatocyte and another terminal ductular cell. Alternatively, it has been proposed recently that bone marrow-derived stem cells are FLSCs since these cells differentiate along the hepatic lineage following colonization of the liver. The intent of this review is to provide insight into the nature and origin of liver stem cells and to explore the possibility that stem cell technology may lead to the development of clinical modalities for the treatment of human liver disease.

Proteome analysis by three-dimensional protein separation: turnover of cytosolic proteins in hepatocytes

We performed a three-dimensional separation of pulse-chase dual-labelled rat liver cytosolic proteins using hydrophobic interaction chromatography, isoelectric focusing, and SDS gel electrophoresis. Due to very different expression rates but similar size and pI of rat liver cytosolic proteins, we demonstrate the impossibility of successful two-dimensional separations of such complex protein mixtures. A pre-fractionation of proteins by hydrophobic interaction chromatography is therefore recommended prior to two-dimensional gel electrophoresis. Our studies confirmed the correlation between protein turnover rates and surface hydrophobicity.

Irniine, a pyrrolidine alkaloid, isolated from Arisarum vulgare can induce apoptosis and/or necrosis in rat hepatocyte cultures

The effects of irniine, a pyrrolidine alkaloid extracted from the tubers of Arisarum vulgare, on rat hepatocyte primary cultures and rat liver epithelial cell line (RLEC) were studied. Cytotoxicity was first evaluated by LDH release, MTT and NR tests and MDA production, while cellular alterations were visualized by electron microscopy and DNA gel-electrophoresis. In hepatocyte and RLEC cultures, a major toxicity appeared at 40 microM of irniine and was demonstrated by an increase in LDH release and decreases in MTT reduction and NR uptake while concentrations lower than 40 microM did not induce significant changes in these parameters. However, we observed an increase in MDA production at 30 microM. Important alterations of the nuclei and mitochondria were also visualized by electron microscopy in cells treated with 50 microM. Using DNA gel-electrophoresis, we demonstrated that irniine at 40 and 50 microM induced DNA damage. All together these results demonstrate that: (1) Irniine induces a significant hepatotoxicity. (2) Irniine toxicity is not mediated by a metabolic derivative since RLEC, which do not contain a monooxygenase system, were also affected by this compound. (3) Irniine induces a significant DNA damage and oxidative stress which leads to cell death by necrosis and/or by apoptosis. Moreover, our data suggest that the alkaloid irniine contained in A. vulgare may be involved in the toxic symptoms observed after medicinal use or consumption of the plant tubers as food both by humans and animals.

Proliferation of lacrimal gland acinar cells in primary culture. Stimulation by extracellular matrix, EGF, and DHT

The study of lacrimal dysfunction and insufficiency, a major cause of dry eye, has been hampered by the inability to induce the proliferation of primary lacrimal acinar cells in vitro. Particularly in light of observations that androgens are able to support the overall size and functional status of the lacrimal glands as well as certain specific lacrimal functions, an in vitro culture system that is permissive for cell proliferation would be most beneficial to study the molecular basis for these processes. Here, we report on the successful establishment of such a system. Using a culture system containing Hepato Stim Medium and Matrigel, we were able to induce the efficient proliferation of primary rabbit lacrimal gland acinar cells with epidermal growth factor (EGF) and dihydrotestosterone (DHT). The generation of this in vitro cell culture system should greatly facilitate study of the regulation of acinar cell function at the molecular and cellular levels.

Occupational hazard evaluation of p-bromobenzyl bromide from tests for genotoxicity

As part of an occupational hazard evaluation, p-bromobenzyl bromide (p-BBB) was evaluated for genotoxic activity in the Ames microbial mutagenicity assay, the alkaline elution assay for DNA strand breaks in rat hepatocytes and the in vitro chromosome aberration assay in Chinese hamster ovary cells. The compound produced equivocal results in the microbial mutagenicity assay but was negative in the alkaline elution assay for DNA strand breaks in rat hepatocytes. The compound produced weakly positive results in the in vitro chromosome aberration assay. There was substantial cytotoxicity in all three assays. It is concluded that p-BBB is weakly genotoxic.

The influence of culture media on embryonic renal collecting duct cell differentiation

During kidney development the embryonic ampullar collecting duct (CD) epithelium changes its function. The capability for nephron induction is lost and the epithelium develops into a heterogeneously composed epithelium consisting of principal and intercalated cells. Part of this development can be mimicked under in vitro conditions, when embryonic collecting duct epithelia are isolated from neonatal rabbit kidneys and kept under perfusion culture. The differentiation pattern is quite different when the embryonic collecting duct epithelia are cultured in standard Iscove's modified Dulbecco's medium as compared to medium supplemented with additional NaCl. Thus, the differentiation behavior of embryonic CD epithelia is unexpectedly sensitive. To obtain more information about how much influence the medium has on cell differentiation, we tested medium 199, basal medium Eagle, Williams' medium E, McCoys 5A medium, and Dulbecco's modified Eagle medium under serum-free conditions. The experiments show that in general, all of the tested media are suitable for culturing embryonic collecting duct epithelia. According to morphological criteria, there is no difference in morphological epithelial cell preservation. The immunohistochemical data reveal two groups of expressed antigens. Constitutively expressed antigens such as cytokeratin 19, P CD 9, Na/K ATPase, and laminin are present in all cells of the epithelia independent of the culture media used. In contrast, a group of antigens detected by mab 703, mab 503, and PNA is found only in individual series. Thus, each culture medium produces epithelia with a very specific cell differentiation pattern.

Effect of hydrazine upon vitamin B12-dependent methionine synthase activity and the sulphur amino acid pathway in isolated rat hepatocytes

The effect of the industrial chemical, hydrazine (4-12 mM), on methionine synthase (EC 2.1.1.13) activity and levels of the sulphur amino acids homocysteine, cysteine, and taurine as well as GSH were investigated in vitro in isolated rat hepatocyte suspensions and monolayers in order to explain some of the adverse in vivo effects of hydrazine. None of the concentrations of hydrazine were overtly cytotoxic in hepatocyte suspensions (measured as lactate dehydrogenase [LDH] leakage) after 3 hr. However, after 24 hr in culture cells treated with 12 mM, hydrazine showed a significant increase in LDH leakage. Methionine synthase activity was reduced by hydrazine (8 and 12 mM) in suspensions (by 45 and 55%, after 3 hr) and monolayers (12 mM; 65-80% after 24 hr). This was not due to nitric oxide production and the inhibitor of nitric oxide synthase, Nomega-nitro-L-arginine, failed to protect against the hydrazine-induced loss of ATP and GSH and the reduction in urea synthesis at 24 hr. Homocysteine export was increased by 6 mM hydrazine, and total taurine content of treated cells was increased by 12 mM hydrazine. Thus, hydrazine was found to have several important and possibly deleterious effects on some parts of the sulphur amino acid pathway.

Bgugaine, a pyrrolidine alkaloid from Arisarum vulgare, is a strong hepatotoxin in rat and human liver cell cultures

Toxicity of bgugaine, a pyrrolidine alkaloid extracted from the tubers of Arisarum vulgare, was studied in three different liver cell culture models: (1) the rat hepatocyte primary culture; (2) a liver epithelial cell line; and (3) the human hepatoblastoma cell line HepG2. Cytotoxicity was evaluated by LDH release, MTT reduction and MDA production. DNA fragmentation was analysed by flow cytometry or DNA gel-electrophoresis. In hepatocyte and epithelial cell cultures, drug toxicity appeared at 30 microM and was evaluated by an increase in LDH release, a decrease in MTT reduction and a higher level of MDA production. Bgugaine concentrations lower than 30 microM did not induce changes in these parameters. In HepG2 cells, bgugaine treatment also induced LDH release at concentrations of 40 and 50 microM. DNA fragmentation, analysed in the HepG2 cell line by flow cytometry, was observed in cultures exposed to 50 microM bgugaine. However, using DNA gel-electrophoresis, we demonstrated that lower bgugaine concentrations (10, 20 and 30 microM) also induced DNA damage. Our results show that: (1) bgugaine induces an important hepatotoxicity; (2) bgugaine toxicity is not mediated by a metabolic derivative; and (3) bgugaine induces a significant DNA damage. Therefore, our data suggest that the alkaloid bgugaine contained in Arisarum vulgarae may be involved in the toxicologic symptoms observed after consumption of this plant tubers by humans and animals.

Making informed choices: medium, serum, and serum-free medium. How to choose the appropriate medium and culture system for the model you wish to create

Complex nutrient mixtures, which are usually called "media," are almost always supplemented with serum, with another complex biological fluid (e.g., milk, embryo extracts, and plasma), or with a defined mixture of hormones and growth factors. The choice of medium and supplements can have a major impact on the growth, function, and even phenotypic and genetic stability of cells in vitro. This choice thus becomes an important part of developing a useful and meaningful in vitro model system. This chapter defines the various roles that the medium plays in supporting cell function and outlines a method for selecting and optimizing medium in growing the cell of choice.

Proposed mechanism for the photodynamic generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine produced in cultured cells by exposure to lomefloxacin

In this study, lomefloxacin (LMX), a widely used quinolone antibiotic with a high frequency of clinical phototoxicity, was investigated by measuring the effects of several antioxidants on its ability to form of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in cultured adult rat liver cells after exposure to UVA. In the current study the observed DNA damage, reflected by the formation of 8-oxo-dG, was almost completely inhibited by co-incubation of LMX and cultured cells with sodium azide (NaN3) that specifically quenches singlet oxygen. Vitamin E (alpha-tocopherol), known to quench both superoxide and singlet oxygen, inhibited 8-oxo-dG formation by approximately 54%. Mannitol, a hydroxyl radical scavenger, inhibited 8-oxo-dG formation by 64%. Butylated hydroxyanisole (BHA), a scavenger of hydroxyl, peroxy and alkoxy radicals, showed no inhibition of 8-oxo-dG formation but in fact enhanced levels of 8-oxo-dG by 169%. The results of this study suggest that the mechanism for the photodynamic generation of 8-oxo-dG by LMX is mediated, at least in part, by both singlet oxygen and hydroxyl radical and involves both type I and type II photosensitization.

A fluoroquinolone antibiotic with a methoxy group at the 8 position yields reduced generation of 8-oxo-7,8-dihydro-2'-deoxyguanosine after ultraviolet-A irradiation

We have previously reported that two fluoroquinolone antibiotics gave rise to 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) in DNA of cells concurrently exposed to UV-A and that this correlated with clinical phototoxicity. To determine the structural basis for generation of oxidative damage, the ability of two synthetic fluoroquinolone candidate antibiotics, Bayer 12-8039 (12-8039) and Bayer Y3118 (Y3118), to give rise to 8-oxo-dG in cultured liver epithelial cells was compared. 12-8039 contains a methoxy group at the 8 position of the quinolone nucleus, whereas Y3118 contains a chlorine group at the same position. Y3118 produced dose-dependent increases in 8-oxo-dG formation in cultured cells after UVA irradiation, whereas the 8-OCH3-substituted 12-8039 produced no increase. Also, after exposure to 20 J/cm2 UVA, UV spectral scans of both compounds revealed that Y3118 underwent photodegradation whereas 12-8039 was stable. These results demonstrate that the presence of an 8-OCH3 group on the quinolone nucleus is important for the reduction of photogeneration of oxidative DNA damage and photodegradation in the presence of UVA irradiation. From this, we suggest that 12-8039 has little phototoxic potential.

Serum-free conditions for the long term growth and differentiation of neoplastic canine keratinocytes

Long term cultures of canine keratinocytes have been established but culture conditions currently used require supplementation with fetal bovine serum (FBS). Unfortunately, FBS contains many non-defined components which may interfere with in vitro studies. This study describes the development of defined serum-free culture conditions for neoplastic canine keratinocytes grown submerged and at the air-liquid interface. Two commercially available serum-free media established for human epidermal cells failed to support canine keratinocyte growth. In contrast, a defined serum-free medium developed in our laboratory successfully supported proliferation of neoplastic canine keratinocytes for at least 40 passages. Cells showed a slower growth rate, but reached similar final densities and were morphologically identical to those cultured in FBS. Grown at the air-liquid interface, the cells reached the same degree of differentiation as in vivo stratified squamous epithelium and cultures grown in FBS. These results demonstrate that canine keratinocytes require different serum-free growth conditions than human cells. Neoplastic canine keratinocyte cultures, grown under serum-free culture conditions, provide an ideal in vitro system for comparative studies of keratinocyte biology and pathogenesis of various dermatoses.

Quinolone antibiotic photodynamic production of 8-oxo-7, 8-dihydro-2'-deoxyguanosine in cultured liver epithelial cells

To study the basis for the phototoxicity of quinolones, a class of synthetic antibacterials, the photodynamic ability to mediate 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxo-dG) formation in cultured cells was measured for lomefloxacin (LMX), which is strongly associated with clinical phototoxicity in humans, and ciprofloxacin (CFX), which has few reports of phototoxicity. Adult rat liver (ARL-18) cells were exposed to the quinolones in the presence of UVA and DNA was extracted and analyzed by HPLC with electrochemical detection. Low levels of 8-oxo-dG were found in the DNA of nonirradiated ARL-18 cells and this was increased up to 6-fold in the presence of either LMX (50-400 microM) or up to 3.6-fold in the presence of CFX (50-400 microM) and UVA (20 J/cm2) when compared to the UVA control. Comparing separate experiments with LMX and CFX, LMX produced greater levels of 8-oxo-dG either after dark exposure or after UVA exposure at 20 J/cm2. Also, LMX and CFX were both shown to photodegrade in the presence of UVA, and it was determined that UVA photoinstability alone does not reflect phototoxic potential. These data suggest that the photodynamic potential of LMX and CFX to produce 8-oxo-dG may relate to their human clinical phototoxicity profile. We suggest that the observed clinical phototoxicity is mediated through a UVA photodynamic effect on the quinolone to form reactive oxygen species in the presence of molecular oxygen. The findings indicate that 8-oxo-dG formation can serve as a marker for the potential phototoxicity of new quinolones.

8-Oxodeoxyguanosine formation in the DNA of cultured cells after exposure to H2O2 alone or with UVB or UVA irradiation

The objective of the present study was to establish whether H2O2 alone or in the presence of UVA or UVB would give rise to formation of the oxidatively damaged DNA base 7,8-dihydro-8-oxo-2'-deoxyguanosine (8-oxo-dG) in cultured adult rat liver (ARL-18) epithelial cells. Hydrogen peroxide alone at 5 mM increased 8-oxo-dG levels by 42% of that of culture control. Compared to culture control, UVB exposure at a dose of 0.63 J/cm2 elevated 8-oxo-dG levels only 8.4%. In the presence of 5 mM H2O2 + UVB (0.63 J/cm2), 8-oxo-dG levels were elevated 155% above culture control suggesting a synergistic effect. A UVA dose of 10 J/cm2 did not elevate 8-oxo-dG levels above culture control. In the presence of 5 mM H2O2 plus UVA (12 J/cm2), 8-oxo-dG levels were elevated 310% above controls compared with an increase of 75.8% above control levels at the same dose in the absence of H2O2. These results reveal that both UVA or UVB can promote H2O2 generation of reactive oxygen species (ROS) in whole cells resulting in an increase in the formation of 8-oxo-dG, although the photodynamic generation of ROS from H2O2 occurs with a much higher efficiency in the presence of UVB. Our study also demonstrates that 8-oxo-dG can be generated in cellular DNA of whole cells exposed to H2O2 and UVA or UVB, indicating that the ROS generated in whole cell systems are long enough lived to migrate to the nucleus and cause DNA damage.

Cytological and biochemical response of R1 cells and isolated hepatocytes from rainbow trout (Oncorhynchus mykiss) to subacute in vitro exposure to disulfoton

Ultrastructural, stereological and biochemical alterations in isolated hepatocytes and the permanent fibrocyte-like cell line R1 from rainbow trout (Oncorhynchus mykiss) exposed to 0, 0.2, 2 and 20 mg/l of the phosphorodithioate pesticide disulfoton (Solvirex, O,O-diethyl S-2-ethylthioethyl phosphorodithioate) for up to 5 days were investigated. In both R1 cells and isolated hepatocytes, distinct dose- and time-dependent morphological alterations including diminished amounts of heterochromatin, proliferation of lysosomal elements, dilation and vesiculation of endoplasmic reticulum cisternae, induction of concentric membrane whorls and an increased amount of lipid droplets could be detected at concentrations of > or = 2 mg/l (R1 cells) and > or = 0.2 mg/l disulfoton (hepatocytes). Additional effects in isolated hepatocytes comprised marginalization of heterochromatin, myelin-like structures attached to mitochondrial membranes, formation of ring-shaped mitochondria, proliferation of smooth endoplasmic reticulum, reduction of rough endoplasmic reticulum, induction of ring-shaped Golgi cisternae, glycogen depletion and occurrence of glycogenosomes. Structural changes in isolated hepatocytes could be correlated to suppression of lactate dehydrogenase, glucose-6-phosphate dehydrogenase, alanine aminotransferase, malic enzyme, esterase as well as glutathione S-transferase, but to a stimulation of 7-ethoxycoumarin-O-deethylase and the rate of lipid peroxidation at concentrations > or = 0.01 mg/l disulfoton. Comparison with data from in vivo experiments with rainbow trout indicate the suitability of in vitro techniques for the evaluation of the toxicological potential of a wide range of ecotoxicologically relevant substances.

Effects of intraperitoneal administration of free and liposome-entrapped doxorubicin on rat peritoneal exudate cell populations

In the present paper effects of i.p. treatment with free or liposome-entrapped doxorubicin (DXR) on rat peritoneal exudate cell (PEC) populations were examined. Two types of DXR-liposomes were used: one type consisting of egg-phosphatidylcholine/phosphatidylserine/cholesterol (molar ratio 10/1/4, mean size approx. 0.3 micron) and the other type of distearoylphosphatidylcholine/dipalmitoylglycerol/cholesterol (molar ratio 10/1/10, mean size approx. 0.8 micron). Dramatically fewer PEC could be recovered from rats given free DXR or DXR-liposomes i.p. (10 mg DXR/kg body weight) 24 h before sacrifice than from control rats. Also the ratio of leukocyte species was modified by treatment with DXR, in free or liposomal form; in both cases the relative number of macrophages tended to increase. HPLC determination of the amount of DXR associated with monolayers obtained by seeding PEC harvested after a single i.p. dose of free DXR or liposomal DXR suggests that peritoneal macrophages are not particularly active in endocytosing DXR-liposomes. It was observed that the peritoneal macrophages phagocytosed DXR-containing granules from degranulating mast cells after both i.p. treatment with free DXR and DXR-liposomes. Decreased yields of PEC following i.p. treatment with free or liposomal DXR as well as an involvement of mast cells in the processing of both free DXR and liposome-encapsulated DXR in the peritoneal cavity may have important consequences for approaches to i.p. chemotherapy.

Sequence of the rat hypoxanthine guanine phosphoribosyl transferase (HPRT) transcriptional promoter region in wild-type and mutant rat liver epithelial cell lines

The hypoxanthine guanine phosphoribosyltransferase (HPRT) gene is mutated by a variety of genotoxic agents in adult rat liver (ARL) epithelial cell lines. By polymerase chain reaction (PCR) amplification and DNA sequencing of rat ARL cell HPRT gene sequences with mouse- and rat-specific oligonucleotides, a large portion of the rat HPRT transcriptional promoter region was sequenced. This region exhibits approximately 60% homology with the corresponding mouse sequence, contains a similar G/C-rich region at its 3' end, and contains a similar series of 6-nucleotide (nt) GGGCGG repeats. To determine if this region is a target for mutation by different genotoxins, HPRT-deficient ARL mutants induced by 2-acetylaminofluorene (AAF), N-methyl-N'-nitro-N-nitrosoguanidine (MNNG), or 7,12-dimethyl-benz[a]anthracene (DMBA) were isolated and studied. A 1003-nt fragment of predominantly HPRT regulatory sequences was amplified by PCR using purified genomic DNA from 17 independent mutants and sequenced directly. None of the 17 mutants examined exhibited any alterations in the transcriptional regulatory region or the 5' untranslated region of HPRT exon 1 after direct sequencing analysis of PCR products. In addition, none of the 2-AAF-induced mutants exhibited differences in in vitro transcription rates as determined by nuclear run-on analysis. These data suggest that regulatory sequences of the HPRT gene are not a primary target for mutation by the genotoxins studied.

Genotoxicity and carcinogenicity testing of 1,2-dibromopropane and 1,1,3-tribromopropane in comparison to 1,2-dibromo-3-chloropropane

The activities of 1,2-dibromopropane (DBP) and 1,1,3-tribromopropane (TBP) were studied in seven genotoxicity assays, (i) SOS-induction in E. coli, (ii) DNA repair in primary rat hepatocyte culture, (iii) the Salmonella/microsome assay, (iv) a host-mediated assay using Salmonella, (v) the somatic mutation and recombination assay in Drosophila melanogaster, (vi) HGPRT-mutagenesis assay in ARL 18 cells, and (vii) micronucleus formation assay in mouse polychromatophylic erythrocytes (PCE), forestomach (FS), glandular stomach (GS), duodenum (D), jejunum (J), cecum (C) and liver (L). The halopropanes were also tested for tumor formation in the fish Danio rerio. DBP was active in assays (ii), (v), (vii FS) and (vii L). TBP was positive in assays (ii) and (iii), strongly positive in (vii L) and borderline positive in (iv). However, neither DBP nor TBP induced tumors in fish, in contrast to the carcinogenic 1,2-dibromo-3-chloropropane. The genotoxicity and potential carcinogenicity of DBP and TBP in mammals is discussed.

The appearance, distribution, and longevity of receptor-[125I]T3 complexes within the nuclei of isolated rat hepatocytes

The nuclei of isolated rat hepatocytes were separable into three receptor compartments based upon their differential salt extractabilities: nucleoplasmic receptors (NP) extractable with 0.15 M KCl, high-salt extractable receptors (HSE) extractable with 0.4 M KCl, and salt-resistant receptors (SR) extractable with 0.4 M KCl/5 mM dithiothreitol. The receptor distribution among the three compartments was approximately NP, 45%; HSE, 30%; SR, 25%. The mean percent occupancy with endogenous T3 of the SR receptors (86%) was higher than the occupancies of the NP receptors (68%) and the HSE receptors (63%). When hepatocytes were pulsed with 3 nM [125I]T3 at 37 degrees C for brief intervals, receptor-[125I]T3 complexes were detectable in all three nuclear compartments within 15 sec. With increasing pulse intervals up to 120 sec, the receptor content of each nuclear compartment increased progressively and without evidence of preferential accumulation in any of the three compartments. To determine the life span and intercompartmental "migration" pattern of nuclear receptors, hepatocytes were pulsed with 3 nM [125I]T3 at 37 degrees C for 2.5 min or 5 min, followed by a chase with a 500-fold excess of nonlabeled T3. The population of receptor-[125I]T3 complexes generated during the pulse was serially recovered at increasing intervals after the chase. The complexes of each compartment dissociated with a half-life of approximately 3 min and manifested no predilection to accumulate in any of the compartments. Exposure of isolated hepatocytes to 3 nM T3 for 5 min or 10 min at 37 degrees C induced no change in the gross intercompartmental distribution of receptors compared to control hepatocytes incubated without T3.(ABSTRACT TRUNCATED AT 250 WORDS)

Iron-saturated lactoferrin as a co-mitogenic substance for neonatal rat hepatocytes in primary culture

We studied the effect of lactoferrin on DNA synthesis in neonatal rat hepatocytes in primary culture to determine if this agent acts as a mitogen in human milk. Thymidine incorporation into the DNA of cultured hepatocytes stimulated by lactoferrin in the presence of insulin and human epidermal growth factor was examined. Iron-saturated lactoferrin increased DNA synthesis of neonatal hepatocytes by 1.5 times and this potency was the same as that of insulin. It significantly enhanced the stimulatory effect of human epidermal growth factor plus insulin; DNA synthesis under these conditions was seven times that of control. Iron-free lactoferrin did not affect DNA synthesis, nor did the exogenous addition of ferric ions. The enhancement of DNA synthesis by iron-saturated lactoferrin was significant for neonatal hepatocytes, but not for adult hepatocytes. These results suggest that iron-saturated lactoferrin, which itself had low mitogenic activity, is a co-mitogenic substance for neonatal hepatocytes in vitro.

Staining with fluorescein diacetate correlates with hepatocyte function

To establish the importance of fluorescein diacetate (FDA) as a viability stain for cultured hepatocytes, we hypothesized that FDA staining would correlate positively with hepatocyte viability and function. Mixtures of live and dead cells were stained with FDA and scanned by flow cytometry. A close correlation was observed between the live cell fraction and percent viability as determined by FDA staining (R2 = 0.962). Hepatocytes were also sorted into low fluorescence and high fluorescence groups. Both albumin production and lidocaine metabolism (P-450 activity) were significantly increased in the high fluorescence group compared to the low fluorescence group. An automated, fluorescence-activated assay was useful for rapid assessment of hepatocyte viability. In addition, the intensity of green fluorescence following staining with FDA correlated well with two specific measures of hepatocyte function.

Effects of various medium formulations and attachment substrata on the performance of cultured ruminant hepatocytes in biotransformation studies

1. A procedure for the isolation and primary culture of hepatocytes from goat and cattle is described. Hepatocyte culture performance was monitored for 51 h by measuring viability, cytochrome P-450 maintenance, dealkylation of scoparone and ethylmorphine, and glucuronidation of phenol red. 2. Culture medium composition is discussed in relation to differences between splanchnic blood composition of ruminant and monogastric animal species. Main differences are in glucose and volatile fatty acid concentrations. Modified Williams' E culture medium did not yield higher culture performance than non-modified Williams' E. 3. Coating of culture dishes with either collagen or fibronectin did not improve culture performance. 4. Williams' E, although developed for rodent cells, proves to be a suitable basal medium for ruminant hepatocytes. In this medium, culture quality is high for at least several days. 5. In cultured goat hepatocytes, biotransformation rate for scoparone amounted to 20 nmol/mg protein per h, for ethylmorphine 96 nmol/mg protein per h and for phenol red 2 nmol/mg protein per h. Biotransformation activity in cow hepatocytes is approximately half that in goat hepatocytes.

Dependency of the in vitro stabilization of differentiated functions in liver parenchymal cells on the type of cell line used for co-culture

The differentiation status in cultures of primary rat liver parenchymal cells was determined by measuring the activities of various xenobiotic metabolizing enzymes. Most enzyme activities dropped rather rapidly in monocultures of parenchymal cells. The protein content and the activities of cytosolic epoxide hydrolase, glutathione S-transferase, and alpha-naphthol UDP-glucuronosyl transferase were, however, well stabilized in 7-day-old co-cultures of parenchymal cells with two different lines of rat liver nonparenchymal epithelial cells (NEC1 and NEC2). Phenol sulfotransferase and microsomal epoxide hydrolase activity were reduced in this coculture system after 7 days to about 30 and 20% of the initial activity. Generally, higher enzyme activities were measured in co-cultures with one specific epithelial cell line (NEC2) as compared to those with the other line (NEC1). C3H 10T1/2 mouse embryo fibroblasts supported the parenchymal cells even better than the two epithelial lines, because the activity of microsomal epoxide hydrolase was also stabilized. Glutathione transferase activity was increased over time in this co-culture system. Our results show that the differentiation status of liver parenchymal cells was much better stabilized in co-cultures than in monocultures but that, depending on the type of cells used for co-culture, great quantitative differences existed. The entire pattern of xenobiotic metabolizing enzyme activities could not be stabilized at the kind of levels found in freshly isolated parenchymal cells.

Restriction fragment pattern analysis of HPRT mutations induced in rat-liver epithelial cells by alkylating and arylating agents

Structural alterations in the hypoxanthine-guanine phosphoribosyl transferase (HPRT) gene in genomic DNA of adult rat-liver (ARL) epithelial cells that were mutated by alkylating and arylating mutagens were studied by restriction enzyme fragment pattern (RFP) analysis. ARL cells were mutated with the direct-acting alkylating agent N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) or the activation-dependent arylating agents 7,12-dimethylbenz[a]anthracene (DMBA) and N-2-acetylaminofluorene (AAF). Alterations in the HPRT gene of at least 10 independent 6-thioguanine-resistant (TGr) clones mutated by each chemical were analyzed using 8 different restriction endonucleases; Hind III, EcoRI, BamHI, XbaI, Hae III, XhoI, MspI and PstI, and a full-length HPRT cDNA as a probe in molecular hybridization. Among the 10 MNNG-induced mutants, the RFPs obtained with most endonucleases displayed no changes, while an altered RFP was found in only one mutant using XbaI. None of the 10 DMBA-induced mutants displayed altered RFPs. Restriction analysis of the 10 AAF-induced mutants showed no abnormality in HPRT gene structure in most restriction digests, while altered RFPs were detected in one mutant using MspI and in two mutants with XbaI digestion. Overall, the studies reveal an absence of major DNA sequence changes in 26 of 30 induced mutants although the mutant phenotype of 4 of the TGr clones can be attributed to gross chromosomal changes or a point mutation at the restriction site. The absence of detectable alterations in the RFPs of the majority of the mutants is strongly suggestive of base substitution as the major molecular alteration underlying the mutant phenotype. The HPRT activity of 14 of 30 mutants was at least 5% of the wild-type level, which is consistent with a structural alteration in the gene product expressed as partial activity of the enzyme. Therefore, the data are interpreted as indicating that in the ARL cells, all 3 mutagens induced primarily localized alterations in base sequences in the HPRT gene together with a few mutations involving large sequence changes.

Primary culture of rat hepatocytes entrapped in cylindrical collagen gels: An in vitro system with application to the bioartificial liver

A static culture model employing cylindrical collagen-hepatocyte gels is reported for large scale testing of conditions relevant to the three compartment hollow fiber bioartificial liver. High density hepatocyte cultivation was achieved by cell entrapment within the collagen-hepatocyte gel. Hepatocyte viability was assessed by vital staining, gel contraction, and insulin utilization. Measures of hepatocyte-specific function included albumin synthesis, ureagenesis, lidocaine biotransformation, and cholate conjugation. Although hepatocyte viability remained stable through the seven day incubation period, hepatocyte functions were not uniformly preserved. Albumin synthesis remained stable, while representative P-450 and conjugation activities decreased with time. This static culture system will facilitate the development of a hollow fiber bioartificial liver which utilizes cylindrical collagen-hepatocyte gels.

Differential stabilization of cytochrome P-450 isoenzymes in primary cultures of adult rat liver parenchymal cells

Cytochrome P-450 dependent hydroxylation of testosterone was measured in 7-day-old cultures of primary rat liver parenchymal cells. Determinations were carried out in monocultures of parenchymal cells and co-cultures of parenchymal cells with rat liver nonparenchymal epithelial cells, or mouse embryo fibroblasts. In the monoculture system, testosterone metabolism was drastically reduced and hardly measurable after 7 days in culture. In the co-culture systems, individual P-450 isoenzymes were stabilized on different levels. P-450s p and presumably c were well preserved, P-450 a was reduced but clearly measurable, P-450 h was totally lost whereas P-450s b and e were not measurable after 7 days (the activities of these isoenzymes however were already low in freshly isolated parenchymal cells). The results were independent of the cell line used for co-cultivation and of the method of parenchymal cell isolation, that is whether collagenase or EDTA was used as the agent for dissociating the cells from the liver. The results showed that the co-cultivation of liver parenchymal cells with other nonparenchymal cells significantly improved the differentiated status of the former. In this cell culture system however, not every parameter was equally well stabilized.

Glutamate uptake in primary cultures of biliary epithelial cells from normal rat liver

Biliary epithelial cells (BEC) were isolated from normal rat liver with high purity (greater than 95%) as revealed by morphological criteria as well as staining for gamma-glutamyl transferase and cytokeratin 19. During cultivation for 96 hr flattening of the cells and a loss of microvilli was apparent, while the cytokeratin 19-positive phenotype was maintained. The BEC contained a sodium-dependent as well as a sodium-independent uptake system for glutamate with high capacity. Both activities increased transiently during cultivation peaking after 72 and 48 hr, respectively. After 72 hr, apparent kinetic constants could be calculated for the sodium dependent (Km = 13.6 mM; Vmax = 388 nmoles/min/mg protein) and for the sodium-independent system. (Km = 10.8 mM; Vmax = 132 nmoles/min/mg protein). The transient increase of both transport systems was suppressed by dexamethasone. The sodium-dependence showed a threshold concentration of about 35 mM sodium. Inhibition by kainate was much less potent for BEC than for hepatocytes. These data indicate that BEC contain transport systems for glutamate different from those in hepatocytes and which may be involved in the intrahepatic reabsorption of glutamate from bile.