Effects of exogenous cholecystokinin and gastrin on the secretion of trypsin and chymotrypsin from yellowtail (Seriola quinqueradiata) isolated pyloric caeca

The humoral control of secretion of the proteolytic enzymes trypsin and chymotrypsin was studied in yellowtail (Seriola quinqueradiata). In vitro trials were performed to investigate the effects of cholecystokinin (CCK) and two commercially available gastrin peptides. Isolated preparations of pyloric caeca/pancreas release trypsin and chymotrypsin when incubated with cholecystokinin (CCK) at 10 μM and gastrin I (G1) at 50 μM after 15 min of incubation. On the other hand, G1 at 10 μM and gastrin-related peptide (G2) did not enhance trypsin and chymotrypsin secretion. The studies concerning the CCK effects at different incubation temperatures have shown that trypsin and chymotrypsin secretion at 25 °C was stimulated by CCK after 15 min, while at 10, 15 and 20 °C the stimulatory effects of CCK were observed only after 30 min of incubation. The CCK effects were increased at higher incubation temperatures and longer incubation periods.