Effect of exogenous cholecystokinin on the discharge of the gallbladder and the secretion of trypsin and chymotrypsin from the pancreas of the Atlantic salmon, Salmo salar L.

The humoral control of release of the proteases trypsin and chymotrypsin was investigated in the Atlantic salmon (Salmo salar L.). Intraperitoneal injection of a purified preparation of the peptide cholecystokinin (CCK) from pig into starved fish produces a dose-dependent release of both enzymes from the pyloric caeca/pancreas tissues which accumulate in the intestinal contents (digesta). It also induces release of the contents of the gallbladder. Isolated preparations of pyloric caeca/pancreas when incubated with CCK release trypsin and chymotrypsin. It is concluded that while a possible role for a neuronal component to the control and regulation of these enzymes cannot be ruled out, humoral control by a CCK-like peptide has been established. The fact that a mammalian-derived extract of CCK induces this response in fish indicates an early evolution and subsequent conservation of this control mechanism in the vertebrates.