A study of the initiation of biliary hyperplasia in rats infected with Fasciola hepatica.

Following infection of rats with Fasciola hepatica, an increase in the number of epithelial cells in the common bile duct, labelled with [3H]thymidine, was detected autoradiographically as early as 5 days post-infection (p.i.). This initial mitogenic effect of the infection was limited to that region of the bile duct lying adjacent to the liver, while the region lying next to the duodenum failed to show any increase in labelling until 41 days p.i. Mechanical contact between the parasite and the biliary epithelium did not occur until 41 days p.i. and the initial hyperplasia was evidently not a result of mechanical irritation. The study serves to emphasize the chemical aetiology of the precocious biliary hyperplasia and to more accurately identify its onset.