Rabbit hepatocytes in primary culture: preparation, viability and use in studies of propranolol metabolism

Preparation of equine isolated hepatocytes

In this study a detailed description of the equine hepatocyte isolation procedure is presented. Livers were obtained from horses slaughtered at the local slaughterhouse. For blood removal and liver preservation the following steps are suggested: perfusion with the oxygenated HBSS (0-2 degrees C, with continuous flow of 500-800 ml/min for 3-6 min), protection from ischemia injury by flushing with ice-cold University of Wisconsin Solution (UW, flow rate of 500-800 ml/min), and finally immersion of the liver lobe in UW solution (2 degrees C) during its transport to the laboratory. For equine isolated hepatocyte preparation a "three-step" perfusion procedure was elaborated: rewarming, chelating and collagenase perfusion. We found optimal cell yield and viability under the following conditions: rewarming with UW (38 degrees C) for 8-14 min, chelating with calcium free Hanks' Balanced Salt Solution (HBSS, 38 degrees C) supplemented with 1 mM ethylene glycol-bis[beta-aminoethyl esther]-N,N,N'N'-tetracetic acid at the flow rate of 450 ml/min for 6 min and enzymatic digestion with HBSS supplemented with 0.1% collagenase at 38 degrees C and 450 ml/min flow rate for 8-27 min. These conditions consistently generated cell harvests of 21 x 10(6)+/-4.86 cells/g of perfused liver tissue with viability of 82.7%+/-10.2.

Effect of increasing selenite concentrations, vitamin E supplementation and different fetal calf serum content on GPx1 activity in primary cultured rabbit hepatocytes

Primary rabbit hepatocytes from 6 week old female New Zealand White rabbits (3.0 x 10(6) viable hepatocytes per treatment) were incubated for 24 h or 48 h with two basic variants of the selenium and vitamin E free DMEM/F12-HAM nutrition medium containing 2.5% or 10% fetal calf serum (FCS). Selenium and vitamin E concentrations of the media were varied by the addition of 0, 10, 50 and 100 ng Se/mL medium as sodium selenite and 100 microg alpha-tocopheryl acetate/mL. Lactic dehydrogenase (LDH) leakage of the hepatocytes was not influenced by the various selenium concentrations of the media, whereas vitamin E addition significantly inhibited LDH release. The activity of cellular glutathione peroxidase (GPx1) was markedly induced by increasing the selenium supplementation of the culture media. Vitamin E supply further enhanced GPx1 induction. In hepatocytes cultivated at the lower serum concentration (2.5% FCS), increasing the selenite concentration of the media raised GPx1 and reduced the intracellular levels of the reduced tripeptide glutathione (GSH). No vectored relation between the selenium concentration of the media and the activity of superoxide dismutase (SOD) could be observed. After both incubation periods (24 h and 48 h) SOD activity was significantly higher in the cytosol of hepatocytes grown in media containing 10% FCS as compared to cells incubated at the 2.5% FCS level. Furthermore, SOD activity was reduced by the addition of vitamin E to the media. In conclusion the results indicate an effective metabolism of rabbit hepatocytes for selenite even in amounts as low as nanograms. A general cytoprotective role for vitamin E can be shown by its ability to decrease LDH leakage and by the reduction of SOD activity.

Time-dependent variations of drug-metabolising enzyme activities (DMEs) in primary cultures of rabbit hepatocytes

In the present study, time-dependent variations of drug-metabolising enzyme activities (DMEs) in primary cultures of rabbit hepatocytes, a species of economic importance in Mediterranean countries, were investigated. Cross-bred rabbits were anesthetised and their livers perfused in situ by a two-step collagenase technique; cells suspensions were filtered, seeded in collagen-coated dishes and cultivated at 37 degrees C in a controlled atmosphere for 24 and 72 h. Cytochrome P450 and b(5) contents as well as the catalytic activity of some P450-dependent monooxygenases were measured in subcellular fractions obtained by differential ultracentrifugation; microsomal proteins were also subjected to immunoblotting, using antibodies to rat P4501A, 2B, 2E1 and 3A isoforms. The activity of some microsomal hydrolytic enzymes was also determined. As regards conjugative enzymes, glutathione content and activities of glutathione S-transferase, uridindiphosphoglucuronosyl-transferase, acetyl-transferase and 1,2-epoxibuthane glutathione transferase were assayed. An overall reduction of the catalytic activity was observed 72 h after plating, reaching in certain instances the level of statistical significance. On the whole, our data confirm those previously reported with hepatocytes obtained from other species; however, the evidence that DMEs were still measurable after 72 h supports the usefulness of this in vitro method for drug metabolism studies in the rabbit as well.

Expression of the Hoxa-13 gene correlates to hepatitis B and C virus associated HCC

To study the Hoxa-13 gene in the liver, we examined its expression by RT-PCR in various liver cell lines, rat livers under different conditions, and human primary hepatocellular carcinomas (HCCs). The gene was found to be expressed in cell lines originating from liver stem-like cells, but not in cell lines originating from hepatocytes and bile duct epithelia. Expression was induced in rat livers after treatment with d-galactosamine, which is known to induce oval cell proliferation, but not after a two-thirds partial hepatectomy (2/3 PH) where induction of oval cell proliferation is thought not to occur. Expression of the gene correlated with human HCC samples associated with Hepatitis B or C virus infection in this small series. These results suggest that the Hoxa-13 gene may provide a potentially useful tool for elucidation of mechanisms involved in lineage-specific differentiation and carcinogenesis of liver stem cells.

An update on high-yield hepatocyte isolation methods and on the potential clinical use of isolated liver cells

Isolated hepatocytes are a suitable system for the study of hepatic physiology and metabolism. They are also used for pharmacological and toxicological studies related to hepatic uptake, metabolism, excretion and toxicity of xenobiotics, as well as morphological and metabolic effects induced in the liver as a result of drug or toxic substance exposure. In this paper, the enzymatic methods for hepatocyte isolation in some mammalian species are reviewed, and methods for evaluating cell purification and assessment of cellular morphology and function are also examined. More recently, interest in hepatocyte transplantation has increased, and the clinical experimentation of hepatocyte-based liver support systems has attracted the attention of scientists and hepatologists. From a clinical perspective, using isolated hepatocytes could be useful both for supporting an acutely devastated liver, a chronically diseased liver, and for correcting genetic disorders resulting in metabolically deficient states. Reports of clinical usage of isolated allogenic hepatocytes in hepatocellular transplantation and of xenogenic liver cells in constructing bio-artificial liver support systems are promising, and are renewing interest in the development of methods for isolation and purification of hepatocytes.

Detection of viral proteins after infection of cultured hepatocytes with rabbit hemorrhagic disease virus

The calicivirus rabbit hemorrhagic disease virus (RHDV), which replicates predominantly in the livers of infected rabbits, cannot be propagated in tissue culture. To enable the performance of in vitro studies, rabbit hepatocytes were isolated by liver perfusion and gradient centrifugation. After inoculation with purified RHDV, more than 50% of the cells proved to be infected. Protein analyses led to the detection of 13 RHDV-specific polypeptides within the infected cells. These proteins were assigned to defined regions of the viral genome, resulting in a refined model of RHDV genome organization.

Metabolism of three pharmacologically active drugs in isolated human and rat hepatocytes: analysis of interspecies variability and comparison with metabolism in vivo

1. The metabolism of the three drugs (Org GB 94, Org 3770 and Org OD 14) was studied in isolated human and rat hepatocytes. The metabolic profiles in rat and human hepatocytes were compared with the available in vivo data in both species. 2. All three drugs were metabolized extensively under the conditions used, both in human and rat hepatocytes, showing both extensive phase I and II metabolism. 3. During 3-h incubation with rat hepatocytes the three compounds were metabolized completely, whereas incubation with human hepatocytes only resulted in partial metabolism, amounting for 58% (Org GB 94), 36% (Org 3770) and 94% (Org OD 14) of the dose. In addition, rat hepatocytes excreted relatively more of the formed metabolites than human hepatocytes. 4. For both species, the metabolites formed in the isolated cells were quite similar to those found in vivo. With respect to Org GB 94 and Org 3770, metabolites were detected in man in vivo and in isolated human hepatocytes that were not found in any of the animal species studied previously. 5. The reflection of interspecies differences in isolated hepatocytes, with respect to both metabolite profiles and human-specific metabolites, renders isolated human hepatocytes a very valuable tool during preclinical drug development.

Clearance by the liver in cirrhosis. II. Characterization of propranolol uptake with the multiple-indicator dilution technique

We studied the steady-state hepatic extraction and single-pass hepatic uptake of propranolol in isolated perfused livers from normal rats and compared these values with those of rats with carbon tetrachloride-induced cirrhosis, rats treated with chlorpromazine (an inhibitor of propranolol metabolism) and rats with acute liver injury. The kinetics of propranolol transport in the liver were characterized by means of the multiple-indicator dilution technique, and estimates of cellular influx, efflux and sequestration rate constants were obtained with a computer fit to the model of Goresky. The outflow pattern of propranolol in the hepatic veins was then resolved into throughput material, which had swept past the hepatocytes along with albumin, and returning material, which had entered the cells but returned in the outflow after escaping metabolic sequestration. The steady-state extraction of propranolol was significantly decreased in the three experimental groups compared with that in controls, but the outflow profile differed within each group. In cirrhotic animals, influx was markedly decreased and the sequestration rate constant remained unchanged; most of the propranolol in the outflow consisted of throughput material. In rats treated with chlorpromazine, the sequestration rate constant was decreased, and propranolol in the outflow was mainly returning material. In rats with acute liver injury, both influx and sequestration rate constants were decreased. Indicator dilution curves for nonsequestered tracers showed a decreased transit time for red blood cells and abnormal diffusion of albumin and sucrose into the space of Disse in cirrhotic rats compared with the other groups.(ABSTRACT TRUNCATED AT 250 WORDS)