Mild bile duct proliferation accompanied by portal fibrosis was found in 8% of the animals (Table 1, Figure 3).
Bile duct proliferation has been associated with toxic injury, parasitism, or periductular fibrosis in terrestrial animals (Kelly 1993; MacLachlan and Cullen 1995) and is therefore a nonspecific reaction to chronic extrinsic and/or environmental factors.
In the present study, we found the following histologic changes in liver tissue from 79 East Greenland polar bears: nuclear displacement, mononuclear cell infiltrations, mild bile duct proliferation accompanied by portal fibrosis, and fat accumulation.
Toxicology 24(2):123-139] found an association between bile duct proliferation and PCB exposure, and also reported that mononuclear cell infiltrates were associated with subacute PCB exposure in cynomolgus monkeys (Macaca fascicularis).
Our findings were not in agreement with such a seasonal fibrosis pattern, however, because portal fibrosis was present with bile duct proliferations in all individuals.