Ornithine Carbamyl Transferase Activity Research Articles

Ornithine carbamyltransferase is a sensitive marker for alcohol-induced liver injury

Background Although mitochondrion-derived markers such as ornithine carbamyltransferase (OCT) and glutamate dehydrogenase (GLDH) have been reported to be good markers for alcohol-induced hepatic injury, their use has been limited due to the notion that mitochondrial markers are less sensitive than cytosol-derived markers. We determined the clinical importance of mitochondrion-derived markers in the evaluation of alcohol-induced hepatotoxicity. Methods Rats were administered alcohol chronically (5–30% ethanol in drinking water with or without high fat diet feeding for 15 weeks) and hepatic damages were evaluated by serum OCT and GLDH, together with other liver enzymes such as alanine aminotransferase and aspartate aminotransferase. Hepatic content of the enzymes was also evaluated in the chronic ethanol feeding model to confirm whether induction of the enzyme in the liver reflects the serum activity. Results The serum activities of OCT and GLDH increased significantly by chronic ethanol feeding while other markers did not. Although the hepatic content of OCT and GLDH also increased, the serum activities did not correlate with the hepatic activities and the extent of increase in the liver was much less than in serum. Conclusions Mitochondrion-derived markers, especially OCT, appeared superior to cytosol-derived markers in the detection of alcohol-induced liver injury.

The effect of nucleic acids on growth, ureagenesis and nitrogen excretion of gilthead sea bream Sparus aurata juveniles

The aim of this trial was to evaluate the effect of dietary nucleic acids on ureagenesis and nitrogen balance in gilthead sea bream juveniles. For that purpose, 5 isonitrogenous (7.25% N) diets were formulated based on fish meal as protein source (FM-control diet) and to partially replace the fish meal nitrogen with two levels of nucleic acids (diets RNA1 and RNA2) or brewers yeast (diets BY1 and BY2). Each diet was fed for 10 weeks, to apparent visual satiety, to triplicate groups of 50 fish each with an average body weight of 12.7 g. Inclusion of nucleic acid N either as brewers yeast or RNA led to significant improvement of feed intake and growth, except for fish fed diet RNA2. There were no differences in final weight between groups fed the yeast- and the RNA-containing diets. Although there was an improvement of growth rate of fish fed the RNA or yeast containing diets, dietary nucleic acid supplementation did not have a clear N sparing effect. At the end of the trial there were no significant differences in whole body composition among groups, except for the lipid content which was significantly higher in fish fed the Y2 diet. Hepatic glutamate dehydrogenase activity levels did not differ among groups. Ornithine carbamyl transferase activities were very low in all groups, but appear to be induced by high levels of dietary RNA. Fish fed the yeast diets exhibited the highest arginase activity of all groups. No increase of uricase activities was observed in fish fed the RNA supplemented diets. Ammonia and urea excretion of fish fed the RNA-including diets was higher or significantly higher than in the other groups. Plasma urea levels were higher in fish fed the RNA diets than in the other groups confirming excretion data in that dietary nucleic acid influenced urea excretion through uricolysis. In conclusion, substitution of N supplied by fish meal by that supplied by brewers yeast had a positive effect on growth performance of sea bream, while dietary nucleic acid supplementation did not have a clear N sparing effect. At a dietary level of 11.5% of RNA extract, there was no improvement of fish performance compared to the control, possibly due to an insufficient capacity of fish to degrade high levels of nucleic acid. Data on excretion and plasma metabolites strongly suggest that purinolysis contributes also to ureogenesis in gilthead sea bream.

Beneficial effects of branched-chain amino acids on altered protein and amino acid metabolism in liver cirrhosis: evaluation in a model of liver cirrhosis induced in rats with carbon tetrachloride

The effect of branched-chain amino acids (BCAA) on the metabolism of protein, amino acids and ammonia was examined in rats with cirrhosis, with a special emphasis on the efficacy of early administration of BCAA. Liver cirrhosis was induced in rats by intraperitoneal injections of carbon tetrachloride (CCl 4). The rats were divided into three groups: early-, late- and untreated. The early- and late-treated groups were given BCAA rich food from the early and late stage of liver cirrhosis, while the untreated group was given standard food throughout. Concentrations of amino acids and ammonia in the plasma and the ornithine carbamyl transferase (OCT) activity in the liver were evaluated, and compared with control group after 15 weeks maintenance. Ammonia was significantly higher in the late- and untreated groups, but not in the early-treated group. BCAA, tyrosine, and methionine were significantly lower in the untreated and late-treated groups. Glutamine increased significantly in the un-, late- and early-treated groups. However, no significant differences were found among three groups. A significant difference was found in 3-methyl histidine (3-MH) between the early- and late-treated groups. This study suggests that the administration of BCAA from early stage of liver cirrhosis inhibits breakdown of protein and improves metabolism of protein, amino acids and ammonia.

Bacterial-like energy metabolism in the amitochondriate protozoon Hexamita inflata.

Hexamita inflata is an amitochondriate flagellated protozoon which inhabits O(2)-limited environments. With the aid of 1H NMR spectroscopy, analysis of the metabolic fluxes in H. inflata grown in complex media under limited O(2) was performed. Almost complete carbon recovery from maltose (the principle carbohydrate source in the medium) catabolism was calculated from the measured increase in concentration of ethanol, alanine, acetate and lactate (and estimated CO(2) production). Difference spectra and amino acid analysis also identified changes in concentration of metabolites belonging to the arginine dihydrolase (ADH) pathway. The enzymes of the ADH pathway were detected in extracts with the following activities (in nmoles min(-1) x (mg of protein) x (-1)): arginine deiminase, 3.30; catabolic ornithine carbamyltransferase (OCT), 1.3; anabolic OCT, 93.0; and carbamate kinase, 1829. The organism metabolized the ornithine produced from catabolic OCT activity to putrescine via ornithine decarboxylase (ODC). The polyamines, spermidine and spermine, were formed by the sequential addition of the aminopropyl group of decarboxylated S-adenosyl-L-methionine (SAM) by the respective polyamine synthases. In addition, asparaginase activity was confirmed in H. inflata, catalysing the deamination of asparagine generating aspartate and ammonia. This study also indicates that, as with other amitochondriate protozoa and some bacteria, the ADH pathway significantly contributes to the energy yield of the cell, particularly under O(2)-limited conditions.

1082 Designer cells for a bioartificial liver-restoring ornithine carbamyl transferase (OTC) activity to HEP G2 cells by transfection and 3-dimensional culture restores urea synthesis to levels

1082 Designer cells for a bioartificial liver-restoring ornithine carbamyl transferase (OTC) activity to HEP G2 cells by transfection and 3-dimensional culture restores urea synthesis to levels

Chemoprevention of 2-acetylaminofluorene-induced hepatotoxicity and lipid peroxidation in rats by kolaviron—A Garcinia kola seed extract

The effect of kolaviron, a mixture of Garcinia biflavonoid 1 (GB1), Garcinia biflavonoid 2 (GB2) and kolaflavanone, used in the treatment of various ailments in southern Nigeria on hepatotoxicity and lipid peroxidation induced by 2-acetylaminofluorene (2-AAF) in rats was investigated. The ability of butylated hydroxyanisole (BHA) to attenuate the toxic effect of 2-AAF was also examined. Kolaviron administered orally to rats at a dose of 100 mg/kg body weight twice a day for 1 week before challenge with 2-AAF (200 mg/kg feed) and continuously for 3 weeks at a single dose of 200 mg/kg body weight reversed the 2-AAF-mediated decrease in final body weight and relative organ weights, especially the liver. BHA was administered at a dose of 7.5 g/kg feed to the animals for 4 weeks. The extract decreased significantly the 2-AAF-mediated increase in the activity of aspartate aminotransferase, alanine aminotransferase, γ-glutamyl transferase and ornithine carbamyl transferase by 58%, 62%, 60% and 67%, respectively. BHA elicited respectively 55%, 63%, 57% and 65% reduction in the 2-AAF induced-increase in the activities of these enzymes. Histological examination of the liver slices correlated with the changes in serum enzyme alterations. Similarly, kolaviron decreased the 2-AAF reduction of 5′-nucleotidase and glucose-6-phosphatase activities by 63% and 60%, respectively while BHA elicited 59% and 61% decrease in the activities of these enzymes. Simultaneous administration of kolaviron with 2-AAF inhibited microsomal lipid peroxidation as assessed by the thiobarbituric acid reacting substances (TBARS) formation by 66%. BHA produced a 64% reduction in TBARS formation. In the present study, kolaviron appears to act as an in vivo natural antioxidant and an effective hepatoprotective agent and is as effective as BHA.

Retrospective evaluation of serum ornithine carbamyltransferase activity as an index of hepatotoxicity in toxicological studies with rats

The sensitivity of elevated serum ornithine carbamyltransferase (OCT) as an index of hepatotoxicity in rats was assessed in different studies conducted over a number of years and originally designed to examine the toxicity or carcinogenicity of a variety of test chemicals and diets. Changes in serum OCT activities were compared with the more widely used clinical endpoints, alanine aminotranserase (ALT) and aspartate aminotransferase (AST). In the first study, rats received a single oral dose of the hepatotoxic and hepatocarcinogenic fungal toxin aflatoxin B 1 (AFB 1). The increase in enzyme levels between control and AFB 1-treated rats was greater for serum OCT than for ALT or AST. This response was similar to the changes in serum enzyme levels in studies where rats ingested a hepatotoxic and hepatocarcinogenic choline deficient (CD) diet. When rats were exposed to the hepatotoxic and nephrotoxic fungal toxin fumonisin B 1 (FB 1) by intraperitoneal injection for 6 days, serum AST and ALT were significantly elevated above control levels while OCT was unaffected. The peroxisome proliferator ciprofibrate caused elevated ALT and AST but not OCT at week 52 of dietary exposure, after the development of liver nodules and tumours. Of the two liver-specific enzymes examined in all of the studies, ALT was more consistently predictive of hepatotoxicity than OCT.

A novel approach to practical enzymology teaching: a conductimetric investigation of arginase, inorganic pyrophosphatase, aliphatic esterase, ornithine carbamyl transferase and argininosuccinate lyase activities from mammalian liver

Kinetic conductivity measurement, run as a microcomputer-controlled workstation with eight independent reaction cells, is shown here to be a simple, cost-effective method for assaying enzymes. The technique is demonstrated with enzymes that can be used as markers for the major subcellular compartments of hepatocytes as a one-day student laboratory class with great potential for variation and development. The method is virtually unknown in enzymology, but could be envisaged as standard apparatus for all biochemical laboratories and teaching classes.

The contribution of the arginine dihydrolase pathway to energy metabolism by Trichomonas vaginalis

The enzymes of the arginine dihydrolase pathway were measured in Trichomonas vaginalis hydrogenosome-deficient lines MR-5 and MR-100, and the parent strain TV 10-02. The activities and substrate affinities of arginine deiminase, carbamate kinase and ornithine decarboxylase were similar for the hydrogenosome-deficient lines and the parent TV 10-02. The activity of catabolic ornithine carbamyltransferase, however, was found to be 5–7-fold elevated in the hydrogenosome-deficient lines; the apparent Km for citrulline was similar for all of the lines. Putrescine biosynthesis by the hydrogenosome-deficient cell lines was found to be significantly higher than the parent. Incubation of strain MR-100 with U-[14C]-arginine resulted in a 5-fold greater amount of 14CO2 liberated compared to the parent strain TV 10-02. Inclusion of the ornithine decarboxylase inhibitor difluoromethylornithine in these incubations reduced the CO2 production of strain TV 10-02 by 42%, but only inhibited the MR-100 strain by 14.5%, indicative that the majority of the CO2 liberated from arginine by this strain is derived from the elevated activity of ornithine carbamyltransferase. Despite the increased flow through the arginine dihydrolase pathway, the energy gain to the parasite is ∼10% of that from glucose, thus, under the growth conditions used in this study carbohydrate metabolism provides the bulk of the ATP for the parasite.

Formation of Paramagnetic Chromium in Liver of Mice Treated with Dichromate (VI)

The formation of paramagnetic chromium in the liver of male mice dosed with K2Cr2O7 (10, 20, and 40 mg Cr/kg) by a single ip injection was investigated by electron spin resonance (ESR) spectrometry. Both Cr(V) and Cr(III) complexes were detected in the mice livers at 15 min to 12 hr after Cr(VI) injection. The time course (15 min-12 hr) for the formation of paramagnetic Cr revealed that the hepatic levels of Cr(V) complexes decreased quickly during the first hour but decreased more slowly over the next 11 hr. However, in contrast to Cr(V), Cr(III) complexes appeared to persist for 12 hr after Cr(VI) treatment based on figures of Cr(III) signal. Thus, Cr(III) may be the ultimate form following reduction of Cr(VI) in liver. The total Cr content in liver of mice dosed with dichromate was also increased in a dose-dependent fashion (10-40 mg Cr/kg). However, Cr content in liver remained at similar levels for 15 min-6 hr, and slightly decreased at 12 hr after Cr(VI) injection. Under the same experimental conditions, hepatotoxicity, as estimated by the increase of serum ornithine carbamyl transferase activity, appeared at 3 hr after 20 and 40 mg Cr/kg of Cr(VI) injection, while 10 mg Cr/kg of Cr(VI) produced no hepatotoxicity even at 12 hr. Predosing with phenobarbital, which increased the hepatic levels of cytochrome P450, resulted in a decrease of the levels of Cr(V) and in a small increase of Cr content, without affecting Cr(VI) hepatotoxicity. On the other hand, pretreatment with buthionine sulfoximine, which depleted hepatic glutathione (GSH) levels, caused a decrease of Cr(VI) hepatotoxicity, but the levels of Cr(V) and Cr in the liver remained unchanged. These results demonstrated that in vivo formation of paramagnetic Cr, in particular Cr(V), in liver of mice is clearly detected and quantified by ESR spectrometry and that hepatic levels of cytochrome P450 and GSH are associated with the induction of biological effects by Cr(VI) in liver in vivo. The results also suggested that the formation of Cr(V) was not the only mechanism involved in the induction of hepatotoxicity by Cr(VI) compounds.

Role of cytochrome P450 in hepatotoxicity induced by di- and tributyltin compounds in mice.

The role of cytochrome P450 in the induction of hepatotoxicity by butyltin compounds such as tributyltin chloride (TBTC) and dibutyltin dichloride (DBTC) was investigated in vivo. The pretreatment of mice with SKF-525A, which decreased hepatic levels of cytochrome P450, suppressed TBTC-induced hepatotoxicity, as estimated by serum ornithine carbamyl transferase activity, whereas pretreatment with phenobarbital (PB), which increased the levels of cytochrome P450, enhanced the hepatotoxicity of TBTC. In the case of DBTC, PB pretreatment enhanced hepatotoxicity, while SKF-525A had no effect. Under these experimental conditions only PB pretreatment was found to increase hepatic levels of tin in mice treated with TBTC. These results suggest that hepatic metabolism of butyltin compounds by cytochrome P450 is more closely related to the induction of hepatotoxicity by TBTC than by DBTC. The active tin compounds formed during hepatic metabolism, which are responsible for induction of hepatotoxicity, will be discussed.

Effect of UV-B (302 nm) irradiation on isolated rat hepatocytes.

The present study aimed to evaluate the effect of UV-B irradiation on the functional integrity, and the metabolic and detoxifying capacity of isolated rat hepatocytes. Isolated rat hepatocytes were irradiated in various doses (400 Jm-2, 600 Jm-2, 800 Jm-2 and 1000 Jm-2). The cells were assayed for total lactate dehydrogenase, Na(+)-K(+)-ATPase, ornithine carbamyltransferase activity (OCT) and urea production capacity. Lactate dehydrogenase and Na(+)-K(+)-ATPase activity were significantly decreased in all four irradiated groups (P < 0.001), whereas viability, OCT and urea production capacity showed no alterations.

Protective effects of thiol compounds on chromate-induced toxicity in vitro and in vivo.

The effects of thiol compounds (L-cysteine ethyl ester, 2,3-dimercaptosuccinic acid, or 2,3-dimercapto-1-propanesulfonic acid) on the toxicity induced by chromate (potassium dichromate) were investigated in HeLa cells and mice. Chromate-induced cytotoxicity evaluated by inhibition of cell growth and chromium content of the cells was diminished by all of the thiol compounds tested when the cells were incubated in the medium with both chromate and one of the thiol compounds. In mice injected ip with a thiol compound immediately after injection of chromate, mortality, ornithine carbamyl transferase activity in the serum, and chromium content in the liver were diminished remarkably compared with mice injected with chromate alone. These thiol compounds also caused an increase of urinary chromium excretion. These results suggest that the thiol compounds tested are useful for treating chromate-induced toxicity when they are given immediately after intake of the metal.

Interactions of ibuprofen with influenza infection and hyperammonemia in an animal model of Reye's syndrome.

We have previously reported that a single meal of an arginine-free diet rapidly induces hyperammonemia in young ferrets and that aspirin administration in conjunction with influenza B infection and arginine-free diet results in clinical and biochemical alterations consistent with Reye's syndrome. The objective of the present study was to test whether ibuprofen administration, either alone or in combination with influenza infection and arginine-free diet, produces a similar effect. Two-mo-old ferrets were inoculated intranasally with influenza B virus, treated with therapeutic doses of ibuprofen, and fed a single meal of an arginine-free diet. Arginine-free diet caused a significant increase in plasma ammonia and a small increase in plasma aspartate aminotransferase activity. All ferrets fed an arginine-free diet recovered within 6 to 7 h after ingesting the diet. Ibuprofen treatment, either solely or in combination with influenza infection, did not produce significant change in the plasma levels of aspartate or ornithine aminotransferase activities. A combination of ibuprofen treatment, influenza infection, and arginine-free diet caused a significant increase in the mortality and plasma ammonia levels. Plasma aspartate aminotransferase and ornithine carbamyl transferase activities were elevated, and liver ornithine carbamyl transferase activity was decreased. However, other mitochondrial enzymes such as ornithine aminotransferase were not altered, whereas the activity of cytoplasmic enzymes such as arginase were decreased. These results suggest that ibuprofen administration resulted in generalized hepatopathy rather than specific mitochondrial injury and Reye's syndrome-like changes associated with aspirin in our previous model.

Inhibitory effect of acyclic retinoid (polyprenoic acid) on the secretion of .ALPHA.-fetoprotein in CCl4-treated rats.

A study was conducted to examine the inhibitory effect of acyclic retinoid (polyprenoic acid) on the secretion of alpha-fetoprotein (AFP) in rats with chronic liver damage induced by CCl4. Oral administration of the compound brought about a significant reduction of serum AFP levels at the time when liver cirrhosis was formed. Acyclic retinoid also decreased the activities of serum aminotransferases and ornithine carbamyl transferase, while it increased serum albumin levels, demonstrating the reduction of hepatic parenchymal damage. Significant negative correlation was observed between serum AFP and albumin levels. This cytoprotective effect of the retinoid on the parenchymal cell may well be related to the inhibition of the synthesis and/or secretion of AFP. No significant side effect was observed, despite a long-term administration of the compound. The present finding will provide a potential scope for the future use of acyclic retinoid for the treatment of chronic liver damage.

Assessment in rats of the gonadotoxic and hepatorenal toxic potential of dibromochloropropane (DBCP) in drinking water

This investigation was undertaken to assess the potential of ingested 1,2-dibromo-3-chloropropane (DBCP) to cause testicular and hepatorenal injury, in light of the paucity of data applicable to risk assessment of DBCP in drinking water. Adult male Sprague-Dawley rats were supplied ad libitum with water containing 0, 5, 50, 100, and 200 ppm DBCP for 64 days. A dose-related decrease in water consumption occurred during the study. The 200-ppm animals drank less than half as much water as controls, consumed less food, and subsequently exhibited significantly lower body weight gain. DBCP ingestion thus was not directly proportional to the level of chemical in the water, although daily and cumulative intake of DCP were concentration dependent. Average daily intake of DBCP for the 64-day exposure period was as follows: 5 ppm = 0.4 mg/kg/day; 50 ppm = 3.3 mg/kg/day; 100 ppm = 5.4 mg/kg/day; 200 ppm = 9.7 mg/kg/day. Blood samples were taken after 2, 4, and 6 weeks of exposure and at the terminal sacrifice and assayed for serum glutamic-oxaloacetic transminase, glutamic-pyruvic transaminase, sorbitol dehydrogenase, and ornithine-carbamyl transferase activities and BUN levels. No evidence of liver damage at any exposure level was indicated by either the clinical chemistry indices or histopathology. Histologic examination revealed an apparent increase in the number of nuclei per renal proximal tubule cross-section in the 200-ppm group, possibly indicative of an increased turnover of proximal tubular cells. A slight, but statistically significant, decrease in absolute testicular weight was manifest in the 200-ppm animals, although the decrease was not significant when testicular weight was calculated as g/100 g body wt. Epididymal sperm counts and serum luteinizing hormone, follicle stimulating hormone, and intratesticular testosterone levels were not altered by any dose of DBCP. A qualitative histopathological examination of the testicular seminiferous epithelium failed to reveal any abnormalities in the spermatogenic process.

Assessment in Rats of the Gonadotoxic and Hepatorenal Toxic Potential of Dibromochloropropane (DBCP) in Drinking Water

This investigation was undertaken to assess the potential of ingested l,2-dibromo-3-chloropropane (DBCP) to cause tes-ticular and hepatorenal injury, in light of the paucity of data applicable to risk assessment of DBCP in drinking water. Adult male Sprague-Dawley rats were supplied ad libitum with water containing 0, 5, 50, 100, and 200 ppm DBCP for 64 days. A dose-related decrease in water consumption occurred during the study. The 200-ppm animals drank less than half as much water as controls, consumed less food, and subsequently exhibited significantly lower body weight gain. DBCP ingestion thus was not directly proportional to the level of chemical in the water, although daily and cumulative intake of DCP were concentration dependent. Average daily intake of DBCP for the 64-day exposure period was as follows: 5 ppm = 0.4 mg/kg/day, 50 ppm = 3.3 mg/kg/day; 100 ppm = 5.4 mg/kg/day; 200 ppm = 9.7 mg/kg/day. Blood samples were taken after 2,4, and 6 weeks of exposure and at the terminal sacrifice and assayed for serum glutamic-oxaloacetic transaminase, glutamic-pyruvic transaminase, sorbitol dehydrogenase, and ornithine-carbamyl transferase activities and BUN levels. No evidence of liver damage at any exposure level was indicated by either the clinical chemistry indices or histopathology. His-tologic examination revealed an apparent increase in the number of nuclei per renal proximal tubule cross-section in the 200-ppm group, possibly indicative of an increased turnover of proximal tubular cells. A slight, but statistically significant, decrease in absolute testicular weight was manifest in the 200-ppm animals, although the decrease was not significant when testicular weight was calculated as g/100 g body wt. Epididymal sperm counts and serum luteinizing hormone, follicle stimulating hormone, and intratesticular testosterone levels were not altered by any dose of DBCP. A qualitative histopathological examination of the testicular seminiferous epithelium failed to reveal any abnormalities in the spermatogenic process.

Lethality and hepatotoxicity of complex waste mixtures

Male F344 rats were exposed by gavage to samples of complex mixtures and evaluated 24 hr later. Seven of the 10 samples caused death at doses ranging from 1 to 5 ml/kg body wt. Eight of the 10 samples were hepatotoxic based on histopathologic evaluation; 6 were centrilobular and 2 were periportal hepatotoxicants. The waste samples exerted toxicity through different mechanisms, as indicated by differences in the severity and lobular location of the tissue damage. Nine of the 10 samples caused an increase in the ratio of liver weight to body weight (relative liver weight). With histopathological evaluation as the criterion, relative liver weight was the single best indicator of hepatotoxicity. Exposure to several of the waste samples increased serum total bilirubin and serum enzyme activities of alanine aminotransferase, aspartate aminotransferase, lactate dehydrogenase, alkaline phosphatase, and ornithine carbamyl transferase. As a battery, but not individually, the serum indicators separated the 8 hepatotoxic samples from the 2 nonhepatotoxic samples. In general, the hepatotoxicity of the waste samples did not appear to be readily predicted from (partial) chemical characterization data. An approach that includes both chemical characterization and biological testing should provide valuable information regarding the hazardous nature of complex wastes.

Mitochondrial urea cycle enzymes in rats treated with sodium benzoate

Since sodium benzoate, which is widely used to treat hyperammonemia its effect on mitochondrial urea cycle enzymes was investigated. its effect on mitochondrial urea cycle enzymes was investigated. Sodium benzoate was administered to urease treated hyperammonemic rats and controls. In both groups no interference with the activity of carbamylphosphate synthetase, ornithine carbamyltransferase and N-acetylglutamate synthetase in the liver could be observed at concentrations of benzoate in plasma found in hyperammonemic patients. Careful monitoring of plasma levels reduces benzoate toxicity as shown in a patient with argininosuccinic aciduria.

UTILIZATION OF MOSAIC ANIMALS FOR THE STUDIES OF HEPATIC CARCINOGENESIS

Properties of hyperplastic hepatic nodules, presumptive preneoplastic lesions of hepatocellular carcinomas, were investigated in mosaic rodents of which livers comprise two genetically-different lineages of cells. In the first experiment, we explored the monoclonality of hyperplastic nodules induced by DEN and phenobarbital in female C3H×spf-ash F1 mice of which livers are composed of hepatocytes with and without ornithine carbamyl transferase (OCT) activity. Simultaneous staining for OCT and γ-glutamyltranspeptidase activities demonstrated that the nodules were composed entirely of one or the other of 2 lineages, representing their monoclonality. The second experiment was carried out to investigate the phenotypic reversion of early hyperplastic nodules by using transplantation system between analbuminemic rats (NAR) and SD×NAR F1 rats. Hyperplastic nodule cells isolated from NAR were transplanted into the liver of SD×NAR F1 rats of which livers are positive for albumin. In those recipient mosaic rats, hyperplastic nodules were virtually negative for albumin and the surrounding nonhyperplastic nodule cells were positive. It became clear that, although hyperplastic nodules express biochemical markers during administration of promoting stimuli, they revert to become phenotypically normal after removal of the stimuli.