Effect of chronically administered cholecystokinin on the nude mouse.

The nude mouse has been used to evaluate the effect of cholecystokinin (CCK) on xenografted tissues, but little is known about long-term actions of cholecystokinin on native organs in this animal. We investigated the impact of chronically administered synthetic cholecystokinin octapeptide on the nude mouse. Six groups of eight animals each received intraperitoneal injections twice daily for 14 days with diluent or a 4-log range of cholecystokinin. Overall health, behavior, and body weight were unaffected by this treatment. Among the seven organs examined at necropsy, pancreas alone showed a dose-related increase in weight. Pancreatic DNA content decreased with increasing dosages of CCK-8, while RNA content exhibited a biphasic response to CCK-8. The only histological abnormality occurred in the pancreas and was confined to the higher doses. These data indicate for the first time the action of CCK on the non-tumor-bearing nude mouse. Unlike other animal models, the nude mouse responds to cholecystokinin administration with pancreatic hypoplasia and hypertrophy, which is accompanied by pancreatitis at higher doses.