Long-term fate of the bile duct cells proliferated during chronic thioacetamide poisoning.
The cell composition of the biliary proliferations induced by thioacetamide administration was investigated. At the end of the intoxication period the main cell types identified among the neoformed bile duct cells were as follows: i) poorly differentiated cells (oval cells) usually arranged in clusters or tiny cords, provided with a great amount of free ribosomes; ii) cells arranged in bile ducts of normal appearance; iii) cells arranged in bile ducts and showing intestinal metaplasia. After withdrawal of TAA most of the biliary proliferations disappeared; in the remaining ones, where the incorporation of 3H-thymidine was still appreciable, significant changes in the bile duct cell composition were evident; in fact whereas the oval cells were no longer identifiable, those suggesting an intestinal metaplasia underwent a relative increment as well as those displaying butyrocholinesterase activity; cells devoid of junctional apparatus and filled with free ribosomes were also seen. Some of the reported finding could support the hypothesis that the biological meaning of the different cell types arisen during intoxication is different; some of them could be due to a reactive hyperplasia, while other could be considered as representing a preneoplastic step.