Abstract
The synthesis, secretion and tissue contents of various gastrointestinal hormones change dynamically during development in rats.
Cholecystokinin (CCK) is one of the gastrointestinal hormones which stimulates gallbladder contraction and pancreatic enzyme secretion and acts as a neurotransmitter. We investigated the changes in synthesis of CCK associated with development of rats using male Wistar rats (1, 2, 4, and 10 months old) . Fasting plasma CCK concentrations, tissue contents and gene expression of CCK in duodenum and cerebrum were measured. CCK was extracted from plasma and tissues by a Sep-Pak C18 cartridge and CCK immunoreactivity was measured by radioimmunoassay using anti-CCK antibody (OAL-656) . Total RNA was isolated from the tissue samples. CCK mRNA was measured by Northern blot and dot blot hybridization. The tissue content and gene expression of CCK were measured predominantly in the rat duodenum and cerebrum.
The plasma CCK concentration following an overnight fast did not change significantly with age. The tissue content and gene expression of CCK in the duodenum increased up to 4 months of age and then remained constant, but those in the cerebrum did not change significantly with age. These results suggest that the development of the CCK synthetic system reaches the adult level earlier in the cerebrum than in the duodenum.
