Abstract

• The present study was carried out to examine the effect of a carcinogen, aflatoxin B₁ on the pathogenesis of the bile duct changes in mice experimentally infected with Clonorchis sinensis metacercariae. A total of 75 male albino mice of the BALB/c strain was used, and divided into 3 group; group I, treated with 1.0ppm aflatoxin B₁ in drinking water alone for 12 weeks; group II, given 50 Clonorchis sinensis metacercariae alone and group III, given 50 metacercariae at the beginning of the 12 week treatment with 1.0 ppm aflatoxin B₁ in drinking water. Three mice were served as untreated-uninfected normal control. All mice were fed the standard protein diet which was synthesized and supplied by the Laborarory of Sam-Lip Food Co. Since the 4th week three mice from each group were removed and sacrigiced at 4 week interval up to the 32nd week. The hepatobiliary tissues were extracted and subsequently prepared for light microscopic examination. The tissue specimens were stained with hematoxylin and eosin. Mice in group I showed no significant changes except the lower degrees of bile ductular proliferation and inflammatory cell infiltration at the portal regions at an earlier stage. In groups II and III there were remarkable together with extensive acute and chronic inflammatory cell infiltrations, cellular atypia and periductal fibrosis from earlier stages. However, in group III the histopathological changes observed were more prominent than those in group II throughout the observation. As the time elapsed, they showed gradual regression with some fluctuations in the degrees. No any evidences of malignant changes of epithelial cells were noted in group II, but in group III the first tumor was found at the 28th week and the second one was at the 32nd week, respectively. Histologically the tumors observed were well differentiated adenocarcinoma of the bile duct. It was appeared that the tumors were of peripheral origin with a tendency of multifocal growth. They also showed an infiltrative growth pattern, increased mucin droplets, increased nuclear-cytoplasmic ratio and nuclear hyperchromatism. No hepatocellular carcinoma was noticed throughout the observation. In conclusion, it was suggested that Clonorchis sinensis infection promotes carcinogenic action aflatoxin B₁, a carcinogenic agent.