Effects of Clonorchis Infection and Carcinogens on Ultratructural Changes of Biliary Epithelial Cells in Rats

The effects of carcinogens, 3'-methyl-4-dimethylaminoazobenzene(3'-MeDAB) and aflatoxin B₁ on ultrastructural changes of biliary epithelial cells in the rats experimentally infected with Clonorchis sinensis were investigated using male rats of the Sprague-Dowley strain. The animals were divided into 5 groups : group I, given 50 Clonorchis metacercariae alone ; group II-a, treated with 0.03% 3'-MeDAB alone for 12 weeks; group II-b, treated with 1.0ppm aflatoxin B₁ alone for 12weeks : group III-a, given 50 metacercariae at the beginning of the 12 weeks treatment with 3'-MeDAB and group III-b, treated with 50 metacercariae plus 1.0ppm aflatoxin B₁. Since the 4th week of experiment, ultrastructures of epithelial cells were observed, using transmission electron microscope. In group I, some elaborate interwoven folds of lateral cytoplasm forming labyrinths of interconnected intercellular space, variety in nuclear shape and marked proliferation and swelling of rough endoplasmic reticulum were characteristic. In groups II-a and II-b, remarkable enlargement of nuclear size, increase of chromatin granules along the inner membrane of nucleus and nucleolar margination were prominent. On the other hand, group III-a or group III-b revealed mostly combined findings of those shown in Clonorchis-infected rats and carcinogen-treated ones. Furthermore, the presence of liver fluke and carcinogen led to neoplastic change. In general, treatment with 1.0ppm aflatoxin B₁ alone(group II-b) or 1.0ppm aflatoxin B₁ plus Clonorchis metacercariae(group III-b) resulted in much earlier onset of alterations than that with 0.03% 3'-MeDAB alone(group II-a) or plus metacercariae(group III-a) throughout the observation. Despite differences in time of onset of alterations, they appeared to be essentially of the same order in cases of groups II-a and II-b, or groups III-a and III-b, respectively. In conclusion, it was clearly evidenced that Clonorchis infection plays an important role as a promotor in cholangiocarcinogenesis in the rats treated with 3'-MeDAB or aflatoxin B₁.