Sexual dimorphism in LEC rat liver: suppression of carbonic anhydrase III by copper accumulation during hepatocarcinogenesis.

We examined age-related changes in the protein expression of carbonic anhydrase III (CAIII) in livers of Long-Evans with a cinnamon-like color (LEC) rats using an agouti color (LEA) rats as controls. The levels of the protein of CAIII in the liver of LEC male rats increased before 20 weeks of age, at the stage of acute hepatitis, and were decreased at 54 weeks of age, while those of CAIII in the liver of LEA male rats were highly expressed at all ages. In the normal LEA rats, CAIII showed sexual dimorphism. The level of CAIII in LEA male rat liver relative to female was four times higher. On the other hand, young LEC rat (at 4-12 weeks) showed a higher protein level of CAIII than LEA rats, and then decreased during development of hepatitis. CAIII mRNA also decreased in the LEC rat liver during hepatocarcinogenesis. The level of CAIII in the tumor region was lower than that in the tumor-free region. Immunohistochemical analysis showed that glutathione S-transferase P (GST-P) was positive and CAIII was negative in the precancerous region. The expression of CAIII was suppressed in cancerous lesions in hepatoma-bearing LEC rat liver compared to uninvolved surrounding tissues. These results indicated that suppression of CAIII accompanied hepatocarcinogenesis and it is a secondary consequence of the high copper levels in the liver.

A deletion mutation of the protein tyrosine phosphatase kappa (Ptprk) gene is responsible for T-helper immunodeficiency (thid) in the LEC rat.

Bone marrow (BM)-derived T-cell progenitors differentiate into CD4 or CD8 single-positive (SP) cells in the thymus. We have previously reported that a single autosomal mutation, thid, causes a defect in the maturation of CD4 SP thymocytes and an abnormality of peripheral helper T cells in the LEC rat. In this study we attempted to identify a gene responsible for the thid mutation. We first performed genetic linkage analysis and mapped the thid locus between Myb and D1Rat392 on Chr 1. In this region we found an approximately 380-kb deletion from intron 3 of the Ptprk gene, which encodes a receptor-like protein tyrosine phosphatase type kappa (RPTPkappa) to intron 1 of the RGD1560849 predicted gene in the LEC rat genome. Reconstitution with syngenic BM cells transduced Ptprk but not the RGD1560849 predicted gene rescued development of CD4 SP cells in the LEC rat thymus. It is confirmed by this result that the Ptprk gene is responsible for the thid mutation in the LEC rat. Our results further suggest that RPTPkappa plays a critical role in the development of CD4 SP cells in the thymus.

Comparison of urinary excretion of phenolsulfonphthalein in an animal model for Wilson's disease (Long-Evans Cinnamon rats) with that in normal Wistar rats: involvement of primary active organic anion transporter.

PURPOSE: The aim of this study was to determine the cause of the decline in phenolsulfonphthalein (PSP) excretion in Long-Evans Cinnamon (LEC) rats. METHODS: The uptake of PSP into rat renal basolateral membrane vesicles (BLMV) was studied. Cyclosporin A (CYA) was used to modulate an ATP-dependent primary active transporter. PSP was intravenously injected into rats with or without CYA. The transcellular transport of PSP was examined by using primary cultured renal proximal tubule cells (PTC). RESULTS: No significant difference was found between the uptake of PSP into renal BLMV of Wistar rats and that into renal BLMV of LEC rats. In the presence of CYA, the urinary excretion and the plasma concentrations of PSP in Wistar rats were decreased and increased, respectively. In primary cultured renal PTC from Wistar rats, the basal-to-apical transport of PSP was greater than that in the opposite direction and the basal-to-apical transport of PSP was substantially reduced by the addition of CYA. However, CYA did not affect the basal-to-apical transport of PSP in PTC from LEC rats. CONCLUSIONS: The results suggest that PSP is transported by primary active organic anion transporter and that the activity level of this transporter is reduced in LEC rats.

No significant differences were observed in the amounts of DNA strand breaks produced by copper between male and female liver cells of long-evans cinnamon (LEC) strain rats.

The amounts of DNA single strand breaks that are oxidative damage produced by copper were examined by comet assay in the liver cells of an inbred strain of Long-Evans Cinnamon (LEC) rats that spontaneously develops fulminant hepatitis. At 4 weeks of age, copper contents in the liver of LEC rats were approximately 30-fold higher than those of WKAH rats that are control rats used in the present study. Copper accumulated in the liver of LEC rats in an age-dependent manner and no significant differences were observed between copper contents in the livers of males and females at each week of age from 4 to 15 weeks. No significant amounts of DNA strand breaks were found in the liver cells of both male and female WKAH rats from 4 to 15 weeks of age. DNA strand breaks were produced in the substantial population of LEC rat liver cells at 10 weeks of age and induced in an age-dependent manner from 10 to 15 weeks of age. The amounts of DNA strand breaks produced by copper accumulation in the liver cells of female LEC rats are not more abundant than those in the cells of male rats, although it has been reported that hepatitis in female rats is more serious than that in male rats.

Histological changes in monoaminergic neurons of Long-Evans Cinnamon rats.

The Long-Evans Cinnamon rat, an animal model of Wilson's disease, is an inbred mutant strain with spontaneous hepatitis isolated from Long-Evans rats. The copper concentration in the brains of Long-Evans Cinnamon rats at 4 weeks of age was lower than that of controls, but higher than that of controls at 20 weeks of age. We investigated the tyrosine hydroxylase and 5-hydroxytryptamine immunoreactive fiber densities in the brains of Long-Evans Cinnamon rats aged 4, 10, and 20 weeks by immunohistochemistry, comparing them with Long-Evans Agouti rats used as controls. Tyrosine hydroxylase immunoreactive fiber densities in the cingulate cortex, hippocampus and cerebellum in Long-Evans Cinnamon rats were significantly lower than those of Long-Evans Agouti rats at 4 and 10 weeks of age. On the other hand, 5-hydroxytryptamine immunoreactive fiber densities in the cingulate cortex, caudate-putamen, hypothalamus, and hippocampus in Long-Evans Cinnamon rats were significantly higher than those of controls at 4, 10 and 20 weeks of age. In the cingulate cortex and caudate-putamen, 5-hydroxytryptamine immunoreactive fiber densities became gradually higher with age. The number of aberrant 5-hydroxytryptamine immunoreactive fibers in the cingulate cortex, caudate-putamen, hypothalamus and hippocampus in LEC rats was significantly higher than that of controls. The number of another type of aberrant 5-hydroxytryptamine immunoreactive fibers, which were detected only at 20 weeks of age in the caudate-putamen in LEC rats was significantly higher than that of controls. These results suggest that age-dependent changes in copper concentrations of Long-Evans Cinnamon rats were related to changes in monoaminergic neuron systems.

Storage of lipid droplets in and production of extracellular matrix by hepatic stellate cells (vitamin A-storing cells) in Long-Evans cinnamon-like colored (LEC) rats.

LEC rats spontaneously develop hepatocellular carcinoma with cholangiofibrosis after chronic hepatitis, but the mechanism of development of the hepatic injury is not clear. To investigate the role of hepatic stellate cells in induction or suppression of hepatic fibrosis, we morphologically examined the liver of LEC rats. Accumulation of copper was analyzed by the Danscher-Timm's sulfide-silver method. Histopathological changes were evaluated by hematoxylin and eosin staining, and by Masson's trichrome method. Activated stellate cells were identified by immunostaining method for alpha-smooth muscle actin. Cytological alterations of the stellate cells were investigated by transmission electron microscopy. To evaluate the lipid content in the stellate cells, we analyzed the area of lipid droplets of the cells by morphometric analysis. Also for evaluation of the changes in the number of stellate cells, the numbers of nucleated stellate cells and parenchymal cells were counted and statistically analyzed. Hepatic parenchymal cells showed excessive accumulation of copper at 5 weeks of age. Submassive necrosis was observed at 19 weeks of age. The liver of LEC rats 1.5 years of age showed cholangiofibrosis and subcellular injury of hepatic parenchymal cells. However, no diffuse hepatic fibrosis was observed in the liver, and hepatic stellate cells around the regions of cholangiofibrosis were negative for alpha-smooth muscle actin. The area of lipid droplets of a stellate cell in the liver of LEC rats was 1.6 to 1.8 times as large as that of normal Wistar rats. The hepatic stellate cells did not participate in the accumulation of collagen fibers around themselves when the cells contained a large amount of vitamin A-lipid droplets, even though the development of hepatic lesions was in progress. Our present data are consistent with our previous hypothesis that there is an antagonistic relationship between the storage of vitamin A and the production of collagen in stellate cells.

Mechanism of enhanced lipid peroxidation in the liver of Long-Evans cinnamon (LEC) rats.

The Long-Evans Cinnamon (LEC) rat is a mutant strain of rats that accumulate copper (Cu) in the liver in much the same way as individuals who suffer from Wilson's disease (WD) and has been suggested as a model for this disease. Lipid peroxidation (LPO) is considered to be involved in the toxic action of Cu in the livers of LEC rats. We investigated the mechanism of LPO in the livers of LEC rats showing apparent signs of hepatitis. Several-fold higher LPO levels were observed in post-mitochondrial supernatant (S-9) fraction of livers from hepatitic LEC rats than in those from Wistar rats. To mimic living cells, we introduced NADPH-generating system (NADPH-gs) into the S-9 incubation system. Thus was ensured a constant supply of NADPH to vital enzymes that may be directly or indirectly involved in the generation and/or elimination of reactive oxygen species (ROSs), such as glutathione reductase (GSSG-R), which require NADPH for their reactions. The levels of LPO in liver S-9 from hepatitic LEC rats were further increased by incubating liver S-9 at 37 degrees C in the presence of NADPH-gs. This increase was inhibited by EDTA, butylated hydroxytoluene (BHT), and catalase (CAT), suggesting that some metal, most likely the accumulated Cu, and ROSs derived from hydrogen peroxide (H2O2) are involved in the increased levels of LPO in the livers of hepatitic LEC rats. The requirement of NADPH-gs for enhanced LPO in the livers of hepatitic LEC rats indicates the consumption of NADPH during reactions leading to LPO. It is known that H2O2, and consequently hydroxyl radical are generated during Cu-catalyzed glutathione (GSH) oxidation. The cyclic regeneration of GSH from GSSG by NADPH-dependent GSSG-R in the presence of NADPH-gs may cause sustained generation of hydroxyl radical in the presence of excess free Cu. The generation of H2O2 in S-9 fraction of livers from hepatitic LEC rats was observed to be significantly higher than that in S-9 fraction of livers from non-hepatitic LEC rats and Wistar rats. Moreover, in addition to the reported decrease in glutathione peroxidase (GPX) activity, we found that CAT activity was markedly decreased in LEC rats with hepatitis. The increased generation of H2O2 with reduced activities of GPX and CAT may result in cellular accumulation of H2O2 in the liver of hepatitic LEC rats. Taken altogether, it is suggested that the accumulated H2O2 undergoes the Fenton-type reaction with also accumulated free Cu, thus generating hydroxyl radical in the livers of hepatitic LEC rats and increasing LPO levels in these animals.