RESUMO
The potential promoting and/or complete carcinogenic activity of a methyl group-deficient (MD) diet lacking methionine, choline, vitamin B12, and folate on liver tumor induction in weanling male F344/NCr rats was examined. Each of 50 rats per group received one injection 20 mg diethylnitrosamine [(DENA) CAS: 55-18-5; N-nitrosodiethylamine]/kg body weight at 4 weeks of age, and then each was maintained on a methyl group-adequate (MA) diet for 52 weeks (groups 2 and 5) or on an MD diet for 15 weeks followed by the MA diet for 37 weeks (group 4). Controls received injections of saline and were maintained on the same two respective diet regimens (groups 1 and 3, respectively). Histologic results from sacrifices at 6, 10, 15, 22, 39, and 52 weeks revealed early development of foci of eosinophilic gamma-glutamyltransferase (GGT)-positive hepatocytes by week 6 in DENA-MD diet-treated rats, with subsequent development of a diffuse hyperplasia of hepatocytes, oval cell proliferation, cholangiofibrosis, nodular cirrhosis, and neoplastic nodule (NN) formation and, at 52 weeks, hepatocellular carcinomas (HCC) in 13 of 15 rats. Similar but significantly fewer lesions were observed at slightly later sacrifice times in the livers of saline-MD diet-treated rats, with development of NN in 5 of 12 rats and an HCC in 1 of 12 rats at 52 weeks. DENA-treated rats on MA diets developed relatively few GGT-positive foci, and none developed any neoplastic lesions. Except for basophilic foci, areas and foci of cellular alteration containing glycogen-rich hepatocytes frequently exhibited diminished uptake of injected iron and decreased glucose-6-phosphatase and ATPase contents focally or throughout. This study indicates that a relatively brief exposure of both untreated and DENA-treated weanling rats to a severely MD diet produces classical preneoplastic and neoplastic lesions in their livers.
Assuntos
Colina/toxicidade , Dietilnitrosamina/toxicidade , Deficiência de Ácido Fólico/patologia , Neoplasias Hepáticas Experimentais/patologia , Fígado/patologia , Metionina/toxicidade , Nitrosaminas/toxicidade , Vitamina B 12/toxicidade , Animais , Peso Corporal , Dieta , Sinergismo Farmacológico , Fígado/efeitos dos fármacos , Masculino , Ratos , Ratos Endogâmicos F344 , Fatores de TempoRESUMO
Portions of 162 naturally occurring neoplasms and 26 nonneoplastic lesions from 93 aged male or female F344/NCr rats were implanted into the left inguinal mammary fat pads of weanling syngeneic recipients. As controls, 95 normal tissues were implanted to the right inguinal fat pad. Transplant recipients were maintained for up to 1 year. Essentially, all types of naturally occurring benign and malignant tumors were successfully transplanted, i.e., grew progressively forming nodules and masses. For the transplants, the latency period preceding palpable growth, tumor growth rate, invasiveness, metastatic rate, and time to death were associated with the degree of histological malignancy of the primary tumor. The tumors which were the most malignant based on these criteria included large granular lymphocyte leukemia, sarcomas, and carcinomas. Fibromas, mammary fibroadenomas, and papillomas were easily transplanted but were not invasive. Endocrine tumors generally were the slowest-growing tumors. This study provides evidence that successful tumor transplantation is only evidence of neoplasia and does not distinguish whether a primary tumor is benign or malignant.
Assuntos
Neoplasias Experimentais/fisiopatologia , Envelhecimento , Animais , Feminino , Leucemia Experimental/fisiopatologia , Masculino , Invasividade Neoplásica , Transplante de Neoplasias , Neoplasias Experimentais/diagnóstico , Neoplasias Experimentais/patologia , Ratos , Ratos Endogâmicos F344RESUMO
The effects of phenobarbital (PB) and amobarbital (AB) on the rate of development of hepatocarcinogenesis induced by N-nitrosodiethylamine (DEN) were studied in mice. Groups of 40 B6C3F1 male mice were injected i.p. at 15 days of age with 5 micrograms DEN/g body wt. Beginning at 4 weeks of age, DEN treated groups were given either normal drinking water or water containing either 0.05% PB or AB for up to 36 weeks. DEN alone induced multiple focal hepatic lesions including hepatocellular foci, hepatocellular adenomas and trabecular carcinomas. Subsequent exposure to PB had a suppressing effect on DEN-induced hepatocarcinogenesis. Hepatocellular foci in PB-exposed mice were significantly smaller in size (area) and fewer in number throughout the study. Also, PB treatment either prolonged the latency period or significantly slowed the rate at which hepatocellular tumors developed in these mice. No such effects were seen in AB-exposed mice; AB neither inhibited nor promoted the development of focal hepatic lesions in DEN-pretreated mice. Possible mechanisms responsible for the inhibition of DEN-induced hepatocarcinogenesis include the feminizing effects of perinatal administration of PB.