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The distribution of the exogenous ^14C-lactate by chinese liverfluke Clonorchis sinensis was investigated by autoradiography. The radioactive substance, Sodium DL-lactate-1-^14C (specific activity 20-40mCi/mM), was obtained from Radiochemical Center, England and this labeled compound was dissolved in Tyrode solution at the concentration of 2.5μCi/ml. This solution was designated as incubation medium. Twenty worms of healthy fluke were incubated in 25 ml Erlenmeyer flask with 10ml of incubation medium. This flask was maintained for 1 hour in Dubnoff shaking incubator at 37℃. After incubation, the flukes were rapidly removed from the flask and freed of exteranl radioactivity by a series of washing in cold Tyrode solution. These flukes were fixed in 10% formalin, dehydrated and embedded in paraffin, and were sectioned at the thickness of 5 microns. Then the specimen mounted slides were covered with Kodak AR-10 stripping film and were exposed for 30 days in cold dark room. After the exposure, the autoradiographs were developed in Kodark D-19 and fixed in Kodark acid fixer. Autoradiographs were then stained with hematoxylin and brought to microscopy. The autoradiographs of C. sinensis showed that there were apparent densities of black silver grains derived from ^14C-lactate in regard to various anatomical structures of the worm. The highest densities of black grains were found in the seminal vesicle and spermatic ducts, subparenchymal cells, pharynx, intestinal epithelium, vitellaria and ovary. Moderate amount of radioactivity was also monitored in the tegument, oral sucker, ventral sucker, intestinal contents, and testes. A week concentration of silver grains can be seen in the reticular tissue, uterus and eggs, spermatheca and the content of seminal vesicle. The possible reasons for the appearance of radioactive substance in respective organs and tissues of this fluke were discussed.
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