WBN/Kob rats. A new spontaneously occurring model of chronic pancreatitis.

Chronic pancreatitis-like lesions are observed in 100% of male Wistar Bonn/Kobori rats. At 3 mo of age, histopathologic examinations of the pancreas revealed a distinct infiltration of inflammatory cells with interstitial edema in the acini. At the same time, periductal and interstitial fibrosis and adenomatous hyperplasia of the ductular epithelium were observed. Extensive fibrotic exudation developed rapidly with age, and irregular destruction of the parenchyma was noted. The only abnormality, prior to the appearance of glycosuria, that could be detected clinically was lower levels, compared to Wistar rats, of BT-PABA excreted in the urine after oral ingestion. These lower levels indicate a decrease in enzyme secretion in WBN/Kob rats. Ultrastructural observations in histologically normal areas at 2 mo of age showed a swelling of mitochondria, indicating that ischemia was associated with the early pancreatic lesions. Serial pancreatographies were performed at 2-8 mo of age. Irregular widenings of the main pancreatic duct and dilations of the smaller ducts were observed already at 2 mo of age, suggesting a stasis of pancreatic juice in the early stages of the disease. It seems that male WBN/Kob rats are a useful model of human chronic pancreatitis, with an unknown mechanism regulated by the sex hormones.