Histopathological and biochemical studies on pancreatic fibrosis in WBN/Kob rats

We investigated the time-course of changes in pancreatic fibrosis accompani ed with pancreatitis in WBN/Kob rats. The areas of fibrosis and fatty repla cement were analysed morphometrically, and biochemical measurements of panc reatic and plasma prolyl hydroxylase and of pancreatic collagenase were ass essed. Male rats showed acute pancreatitis at 2-3 months of age, lesions th at later underwent a transition to widespread fibrosis, The fibrosis then d ecreased, and the fibrotic tissue was replaced with adipose tissue. Morphom etrically, the fibrotic area reached its maximal size when the rats were 4 months old, diminishing thereafter. The fibrosis occurred mainly in the int ralobular space, and was principally attributable to type-III collagen. Typ e-I collagen scarcely appeared throughout the experimental period. alpha-sm ooth muscle actin appeared in and around myofibroblasts that developed in a n early stage and diminished later in accordance with the progressive manne r of fibrosis. The plasma prolyl hydroxylase level was higher in males than in females from 4 through 10 months of age. Pancreatic collagenase activit y in the males also increased during the same period. These findings sugges t that pancreatic fibrosis in male WBN/Kob rats is affected by the balance between prolyl hydroxylase and collagenase.