Transferrin receptor expression of the hyperplastic lesions of hepatocyte in experimental hepatocarcinogenesis

Transferrin receptor (TR) performs the major function of binding and internalizing its specific iron-loaded ligand, transferrin, and its expression is closely linked to the proliferation status of the cell. This study was undertaken to elucidate TR expression in the hyperplastic lesion of hepatocyte in chemically induced hepatic carcinogenesis. The resistant hepatocyte model was chosen for a rat model of carcinogenesis and Sprague-Dawley rats were divided into the following groups: the control groups of normal diet and iron-rich diet with or without hydroxyquinoline and the groups of carcinogen alone and carcinogen plus iron-rich diet with or without administration of hydroxyquinoline. Microscopic changes in the liver, expression of transferrin receptor and glucose-6-phosphatase were studied. The hepatocyte of the control group showed both cytoplasmic and membranous expression of TR. The liver of rats fed on high iron diet accumulated iron and the expression of TR was down regulated by intrahepatic iron accumulation. In the carcinogen administered group the resistant hepatocyte of hyperplastic lesion revealed strong membranous expression of TR and failed to accumulate iron in spite of high iron diet but in contrast the surrounding non-resistant hepatocyte expressed TR in both the membrane and cytoplasm and stored iron when fed on high iron diet. The strong membranous expression of TR is one of the characteristics of the resistant hepatocyte of hyperplastic lesion and it seems to be related to the inability to accumulate iron in spite of a high iron diet.

Development of altered hepatocyte foci by separate and combined treatments with radiation and diethylnitrosamine in neonatal rats

To establish an in vivo radiation carcinogenesis model using glutathione S-transferase placental form positive (GST-P+) hepatic foci, newborn rats were irradiated once by 0.5 Gy and 2 Gy of gamma ray or 0.15 Gy and 0.6 Gy of neutron with or without 0.05% phenobarbital (PB). When the rats were sacrificed at the 12th or 21st week, the incidence of GST-P+ foci induction by radiation alone was very low. The neutron was more sensitive than the gamma ray at week 12 and the reverse phenomenon was observed in the groups at week 21. PB combination showed an increased incidence of GST-P+ foci in gamma ray irradiated groups. The neutron irradiation combined with PB did not show any significant difference compared with the corresponding PB untreated groups. We also investigated the combined effect of diethylnitrosamine (DEN) and 0.75 Gy of gamma ray irradiation. Intraperitoneal injection of 0.15 mumol/g body weight of DEN at 1 hour after gamma ray irradiation showed significantly increased the number and area of GST-P+ foci compared with those of DEN alone or DEN at 1 hour before gamma radiation (P < 0.001). From these data, after more defined experiments, an in vivo radiation carcinogenesis model will be established by radiation alone or a combination of radiation and carcinogens.

Short-term Effect of Iron on the Hyperplastic Lesions of Chemical Hepatocarcinogenesis

This study was undertaken to elucidate the short-term effect of iron on the hyperplastic lesions of experimental hepatocarcinogenesis. The Solt-Farber's resistant hepatocyte model was chosen for the experiment, and Sprague-Dawley rats wee divided into six groups: normal control, iron-rich diet administration with or without hydroxyquinoline. The iron content, microscopic changes, bromodeoxyuridine(BrdU) labelling index and the DNA polidy were studied. In the carcinogen administered group, oval cell proliferation and consecutive hyperplastic lesions of hepatocyte developed regardless of iron administration. The hepatic iron content was increased rimarkably by iron administration, but gradually decreased as the hyperplastic lesions developed in carcinogen administered groups. Although the administration of iron without carcinogen induced hepatic accumulation of stainable iron, the hyperplastic lesions appeared to be lack of it. BrdU labelling indices of the oval cells and the hyperplastic lesions of hepatocyte were very high and were not significantly altered by iron administration. Most liver cells had diploid or tetraploid DNA content, but there was an increase of diploidy as the development of hyperplastic lesions regardless of iron administration. The results indicate that the chemical carcinogen-induced hyperplastic lesions of hepatocyte do not accumulate iron, and that short-term iron administration does not affect the development of hyperplastic lesions and their proliferative activity and DNA ploidy.

The effect of deferoxamine on the preneoplastic lesions in the chemically induced hepatocarcinogenesis

Iron is essential for the growth of all living cells. One of the most important intracellular roles of iron is the activation of ribonucleotide reductase, which is indispensible to the production of deoxyribonucleotide necessary for DNA synthesis. Deferoxamine (DFO) is an iron chelating agent and has been known to have an antiproliferative effect in various malignant cells including hepatocellular carcinoma and the effect seems to be related to depletion of iron. This study was undertaken to investigate the effect of DFO on preneoplastic lesions in chemically induced hepatocarcinogenesis. The resistant hepatocyte model was used and Sprague Dawley rats were divided into the following groups; I: normal control, II: carcinogen administered group, III: carcinogen and DFO administered group. Rats were sacrificed at 3 days, 1 week, 2 weeks, 3 weeks, 4 weeks and 8 weeks after partial hepatectomy (PH). DFO (50 mg/kg/day, I.P.) was daily injected from 3 weeks before administration of carcinogen to the time when rats were sacrificed. Hepatic iron content was higher in group II than in group III, especially at 3 days and 1 week after PH. Hyperplastic lesions of resistant hepatocytes were less well developed in group III than in group II. Bromodeoxyuridine labelling indices of oval cells and hyperplastic lesions of resistant hepatocytes were higher in group II than in group III except for rats examined at 3 days after PH. The results suggest that DFO has an antiproliferative effect on preneoplastic lesions in hepatocarcinogenesis and it might be related to reduction of the hepatic iron.

The Effect of Copper on 3'-Methyl-4-dimethylaminoazobenzene Induced hepatic Carcinogenesis

To elucidate the effect of copper on the 3'-methyl-4-dimethylaminoazobenzene(3'-MeDAB) induced hepatic carcinogenesis, Sprague-Dawley rats were divided into 4 groups according to 3'-MeDAB and copper administration: I. noraml control, II. copper only, III. 3'-MeDAB only, IV. 3'-MeDAB plus copper. The animals of groups III and IV were fed experimental diet containing 0.06% 3'-MeDAB. Copper was administrated intraperitoneally in a dose of 0.5 mg, twice a weak. Animals were sacrificed at different intervals. Liver weight, hepatic copper content and gross and microscopical changes of the liver were examined and the cell kinetics of various lesions in the hepatic carcinogenesis was studied by applying the immunohistochemical method for bromodeoxyuridine(BrdU). The hepatic copper content was significantly increased in animals given copper but returned to the normal value after cessation of adminstration. 3'-MeDAB administration caused oval cell proliferation and produced hyperplastic nodules, cholangiofibrosis and carcinoma of the liver. Simultaneous administration of copper did not alter the incidence of 3'-MeDAB induced lesions, except for carcinoma. The liver weight and the size of hepatic nodules and masses were smaller in group IV than in group III. The liver weight as well as the nodularity and the mass formation continued to increase affect cessation of 3'-MeDAB administration. Copper did not affect the BrdU labelling indices of the hepatic lesions induced by 3'-MeDAB. The oval cell proliferation and the BrdU labelling indices of the oval cell and the hyperplastic nodule were decreased, but the incidence of cholangiofibrosis and its BrdU labelling index were still elevated after cessation of 3'MeDAB administration. These findings indicate that copper could delay the developement of 3'-MeDAB induced hepatic lesions, but not suppress, since copper does not stay long enough to accumulate in the rat liver, and that copper could not affect the proliferation of 3'-MeDAB induced hepatic lesions once developed.