Cellular proliferation of bile ductules and gamma-glutamyl transpeptidase in livers and sera of young cattle following a single infection with Fasciola hepatica.

During the course of experimental single infection with Fasciola hepatica in calves, the origin of the increased concentration of gamma-glutamyl transpeptidase (gamma-GT) found to be present in the serum during the biliary stage of the disease, was studied. The enzyme originates from the liver after flukes have caused intermittent and selective cholestasis in the bile-duct system. The enzyme which normally is present in the bile ducts can under these circumstances enter the surrounding interstitial tissues through broken-up junctions of the bile drainage system or be added to these from proliferating bile-ductule epithelium. The multiplication of bile-ductule cells can be looked upon as a neogenesis of cholangioles, which becomes essential when newly formed perilobular connective tissues prevent restoration of the anatomical connections of the bile capillaries with the biliary tree. The connective tissue growth is induced by bile fluid. An initially regional perilobular fibrosis is eventually distributed diffusely through the liver by migration of flukes. The continued and extending fibrosis is due to the constant recurrence of intermittent and selective cholestasis. The transient occlusions of branches of the bile ducts are very likely to be attributable to persistent cholangitis. The growth of connective tissues has a considerable effect on the gain in weight of the liver.