In developmental terms, the endocrine system of neither the gut nor the pancreatic islets has been characterized fully. Little is known about the involvement of cholecystokinin (CCK), a gut hormone, involved in regulating the secretion of pancreatic hormones, and pancreatic growth. Here, we tracked CCK-expressing cells in the intestines and pancreata of normal mice (BALB/c), Non Obese Diabetic (NOD) mice and interferon (IFN)-gamma transgenic mice, which exhibit pancreatic regeneration, during embryonic development, the postnatal period and adulthood. We also questioned whether IFN-gamma influences the expression of CCK. The results from embryonic day 16 showed that all three strains had CCK in the acinar region of pancreata, and specifically in alpha cells that also expressed glucagon. However, in adulthood only BALB/c and NOD mice continued this pattern. By contrast, in IFN-gamma transgenic mice, CCK expression was suppressed from birth to 3 months of age in the pancreata but not intestines. However, by 5 months of age, CCK expression appeared in the regenerating pancreatic ductal region of IFN-gamma transgenic mice. In the intestine, CCK expression persisted from fetus to adulthood and was not influenced by IFN-gamma. Intestinal cells expressing CCK did not co-express glucagon, suggesting that these cells are phenotypically distinct from CCK-expressing cells in the pancreatic islets, and the effect of IFN-gamma on CCK varies depending upon the cytokine's specific microenvironment.
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