To determine the adequate models for studying the functions of pancreatic acinar cells, secretory responses to CCK and to CCK receptor antagonist, L-364, 718 were examined in freshly isolated cells and confluent monolayer cells. The results showed that as CCK concentration increased, releases of amylase and lipase increased dose-dependently reaching a maximum at 10^-9 M in acinar cells cultured in serum-containing media as well as in serum-free media. Acinar response to CCK was partially inhibited by L-364, 718, L-364, 718 itself had no effect on the releases of both amylase and lipase. Confluent monolayer of acinar cells released relatively low levels of enzymes and exhibited less response to CCK. In conclusion, short-term culture of acinar cells would be suitable to study the regulation of pancreatic enzyme secretion, and serum factors do not influence acina response to the secretagogues. However, confluency of the acinar cells resulted in the loss of their secretory potential in the aspect of amylase and lipase release.