Oncogenes in mouse liver tumors.
Explore the source record for details and available documents.
Animals↗
Biomedical subjects
T Devereux
Publications and source records attributed to T Devereux.
Functional and structural zonal hepatocyte heterogeneity--dynamics and ontogenic development.
Explore the source record for details and available documents.
Animals↗
Separation and characterization of hepatocytes from immature and adult rats into distinct subpopulations by centrifugal elutriation.
Hepatocytes were isolated from immature and adult rat liver by retrograde perfusion with calcium free buffer, followed by enzymic digestion, and separated into subpopulations by centrifugal elutriation. Several subpopulations with increasing cell diameters were distinguished. The smaller cells were attributed to the periportal area, the larger ones to the perivenous (centrilobular) region. Profiles of total cytochrome P-450 concentration, benzphetamine N-demethylation and ethoxyresorufin O-deethylation, NADPH-cytochrome c-reductase, glucose-6-phosphatase and glutamate-pyruvate-transaminase activities were determined in all subpopulations. With adult hepatocytes an increasing cytochrome P-450 concentration with increasing cell diameter (increasing from periportal to perivenous hepatocytes) could be observed, paralleled by increasing activities of benzphetamine N-demethylation and ethoxyresorufin O-deethylation activities. While NADPH-cytochrome c-reductase did not show a distinct zonation, glucose-6-phosphatase and glutamate-pyruvate-transaminase revealed increasing activities with increasing cell diameter. Immature hepatocytes (rats aged 11-15 days) were smaller, and more fragile. They could not be isolated with the same enzyme solution as adult hepatocytes and they did not show any zonation of cytochrome P-450 concentration, although the zonation of benzphetamine N-demethylation and ethoxyresorufin O-deethylation was almost fully developed. For NADPH-cytochrome c-reductase a zonation with higher activities in the perivenous cells could be demonstrated, in contrast to the lack of zonation in adult rats. Glucose-6-phosphatase activity showed a decline with increasing cell diameter in immature hepatocytes, whereas glutamate-pyruvate-transaminase activity did not show any zonation. In rats aged 20 days the zonation of these parameters in liver was in between that of younger and older animals. Zonation of the liver lobule develops postnatally with individual patterns for the different parameters.
Aging↗
Functional hepatocellular heterogeneity determined by the hepatotoxins allyl alcohol and bromobenzene in immature and adult Fischer 344 rats.
Adult (male, 75-90 days old) and immature rats (both sexes, 11-12 days old) were treated with allyl alcohol or bromobenzene to induce periportal or centrilobular hepatic injury, respectively. Histologically confirmed liver lesions were produced in adult rats with both treatments. In adult rats, allyl alcohol decreased hepatic cytochrome P-450, benzphetamine N-demethylation, and ethoxyresorufin O-deethylation activities all by about 30%, whereas bromobenzene influenced these parameters differently: cytochrome P-450 was lowered by 55%, benzphetamine N-demethylation by 80%, and ethoxyresorufin O-deethylation by 90%. Cytochrome c reductase, 5'-nucleotidase, glucose-6-phosphatase, and glutamate-pyruvate transaminase activities were not significantly influenced. In immature rats, allyl alcohol did not produce histopathological alterations in liver, but did lower both cytochrome P-450 concentration (30%) and ethoxyresorufin O-deethylation (75%). Benzphetamine N-demethylation was not significantly affected. Bromobenzene produced typical centrilobular liver damage and a decrease of both cytochrome P-450 (20%) and ethoxyresorufin O-deethylation (50%). Benzphetamine N-demethylation was increased slightly, but not significantly. The differences in effects of the two hepatotoxins in adult vs immature rats seem to indicate that the hepatocellular heterogeneity of xenobiotic metabolism which is seen in adult liver (perivenous vs periportal areas) is not well developed in the immature animal.
1-Propanol↗
Separation of immature and adult rat hepatocytes into distinct subpopulations by centrifugal elutriation.
Several subpopulations of hepatocytes with increasing cell diameters were isolated, the smaller cells were attributed to the periportal area, the larger ones to the perivenous region. Profiles of total cytochrome P-450, benzphetamine N-demethylation and ethoxyresorufin O-deethylation, cytochrome c-reductase, glucose-6-phosphatase and GPT activities were determined. With adult hepatocytes an increasing cytochrome P-450 concentration with increasing cell diameter could be observed, paralleled by increasing activities of monooxygenases. Glucose-6-phosphatase and GPT also revealed increasing activities with increasing cell diameter, but cytochrome c-reductase did not show a distinct zonation. Immature hepatocytes (age 11-15 days) were smaller, more fragile, and could not be isolated with the same enzyme solution as adult hepatocytes. They did not show any zonation of cytochrome P-450 whereas the zonation of the monooxygenases was almost fully developed. For cytochrome c-reductase a zonation with higher activities in the perivenous cells could be demonstrated, in contrast to the lack of zonation in adult rats. Glucose-6-phosphatase showed a decline with increasing cell diameter in immature hepatocytes, whereas GPT did not show any zonation. In rats aged 20 days the zonation of these parameters in liver was in between younger and older animals.
Alanine Transaminase↗
Prostaglandin synthetase and cytochrome P-450-dependent metabolism of (+/-)benzo(a)pyrene 7,8-dihydrodiol by enriched populations of rat Clara cells and alveolar type II cells.
The metabolism of (+/-)-trans-7,8-dihydroxy-7,8-dihydrobenzo(a)pyrene (BP-7,8-diol) by prostaglandin synthetase and cytochrome P-450-dependent monooxygenases was studied using enriched fractions of Clara cells and alveolar type II cells from rat lung. Arachidonic acid-fortified fractions enriched in Clara cells and alveolar type II cells metabolized BP-7,8-diol to the 7,10/8,9-tetrol of benzo(a)pyrene and the 7/8,9,10-tetrol of benzo(a)pyrene. These tetrols are formed upon solvolysis of (+/-)-7 beta, 8 alpha-dihydroxy-9 alpha, 10 alpha- epoxy-7,8,9,10-tetrahydrobenzo(a)-pyrene (BP diol-epoxide I). Arachidonic acid-dependent metabolism of BP-7,8-diol to BP diol-epoxide I in enriched Clara cells and alveolar type II cells was completely inhibited by indomethacin, a classical inhibitor of prostaglandin synthetase. Enriched Clara cells and alveolar type II cells also metabolized BP-7,8-diol to BP diol-epoxide I in the presence of NADPH. Amounts of BP diol-epoxide I-derived tetrols formed from BP-7,8-diol by the prostaglandin synthetase-dependent and the cytochrome P-450-dependent pathways varied significantly between the two pulmonary cell fractions examined. In fractions enriched in Clara cells, cytochrome P-450-dependent BP-7,8-diol oxidation was higher than was prostaglandin synthetase-dependent BP-7,8-diol oxidation; while in fractions of alveolar type II cells, prostaglandin synthetase-dependent BP-7,8-diol oxidation to BP diol-epoxide I predominated. Pretreatment of rats with beta-naphthoflavone resulted in a 2- to 3-fold increase in BP diol-epoxide I formation by prostaglandin synthetase and cytochrome P-450-dependent monooxygenases in both enriched Clara cells and alveolar type II cells. These increases in BP-7,8-diol oxidation to BP diol-epoxide I appear to be due to induction of the two enzymatic pathways in both pulmonary cell types. No qualitative changes in the pattern of BP-7,8-diol metabolism by either enzymatic pathway in enriched Clara cells or alveolar type II cells were observed following beta-naphthoflavone treatment. The results suggest that pulmonary prostaglandin synthetase may serve as either an additional or an alternative bioactivating enzyme to the cytochrome P-450-dependent monooxygenases for the formation of reactive chemical carcinogens in the lung.
Animals↗
Cellular and subcellular localization of a binding protein for polychlorinated biphenyls in rat lung.
Enriched cell populations from rat lung were isolated by use of elutriation. An in vitro ligand binding assay as well as a Western immunoblot assay were used to determine the levels of a binding protein for certain polychlorinated biphenyls (PCBs) in cytosolic preparations from these cell populations. The cell population enriched in Clara cells (30% Clara cells) contained by far the largest amount of the PCB-binding protein, 759 +/- 81 pmol/mg of cytosolic protein as judged by an in vitro ligand binding assay. Western immunoblot analysis of cytosolic preparations from the enriched cell preparations, using antibodies to the PCB-binding protein, showed levels of immunoreactive material in these fractions that corresponded to the level of the PCB-binding protein as determined by the in vitro ligand binding assay. By use of the peroxidase-antiperoxidase method of immunoperoxidase staining, antibodies to the PCB-binding protein were found to stain the Clara cells in sections of paraffin-embedded rat lungs. Intense immunoperoxidase staining of the material lining the airway epithelium was also observed. The protein was predominantly localized to the secretory granules in the apical cytoplasm of the Clara cells as determined using antibodies to the protein, protein A-gold, and electron microscopy. Previous studies have shown a selective in vivo accumulation of methylsulfonyl-PCBs in Clara cells of rodent lung and the present investigation, demonstrating the presence in the Clara cells of a secretory Mr 13,000 protein that binds methylsulfonyl-PCBs with high affinity, gives further support to the contention that the protein is an important factor in determining the in vivo disposition of these compounds.
Animals↗