The effect of unsulfated cholecystokinin on pancreatic growth was evaluated in two experimental models in vivo and in vitro. Mice were injected with sulfated cholecystokinin (CCKs) or unsulfated cholecystokinin (CCKu) (10 or 20 micrograms/kg) or vehicle twice daily for 15 days. Animals were then killed and pancreatic weights, protein, amylase, and DNA content were evaluated. In vitro, growth was evaluated by DNA synthesis and viable cell counts. MIA PaCa-2 and BxPC-3 human pancreatic cancer cells were treated with CCKs or CCKu (10(-12) to 10(-9) M) for 48 or 72 h in the presence of [3H]thymidine to evaluate DNA synthesis. Viable cell counts were performed on both cell lines grown in the presence or absence of unsulfated CCK (10(-12) to 10(-9) M) for 96 h. Pancreatic weight, protein, amylase, and DNA were significantly increased in animals treated with either CCKs or CCKu. However, pancreatic weight, protein, and amylase were significantly higher in mice treated with CCKs compared to CCKu (p less than 0.005). DNA content and index of hyperplasia were the same whether mice were treated with CCKs or CCKu. CCKu was as potent a stimulus for DNA synthesis as CCKs in MIA PaCa-2 and BxPC-3 cells. Finally, CCKu increased cell counts in both pancreatic cancer cell lines. These data suggest that the mechanisms responsible for CCK-induced growth of normal pancreas and pancreatic cancer may differ from those that regulate secretion.