Physiology of the endocrine pancreas

Characterization of Insulin-Immunoreactive Cells and Endocrine Cells Within the Duct System of the Adult Human Pancreas

OBJECTIVE

The adult pancreatic duct system accommodates endocrine cells that have the potential to produce insulin. Here we report the characterization and distribution of insulin-immunoreactive cells and endocrine cells within the ductal units of adult human pancreas.

METHODS

Sequential pancreas sections from 12 nondiabetic adults were stained with biomarkers of ductal epithelial cells (cytokeratin 19), acinar cells (amylase), endocrine cells (chromogranin A; neuron-specific enolase), islet hormones (insulin, glucagon, somatostatin, pancreatic polypeptide), cell proliferation (Ki-67), and neogenesis (CD29).

RESULTS

The number of islet hormone-immunoreactive cells increased from large ducts to the terminal branches. The insulin-producing cells outnumbered endocrine cells reactive for glucagon, somatostatin, or pancreatic polypeptide. The proportions of insulin-immunoreactive count compared with local islets (100% as a baseline) were 1.5% for the main ducts, 7.2% for interlobular ducts, 24.8% for intralobular ducts, 67.9% for intercalated ducts, and 348.9% for centroacinar cells. Both Ki-67- and CD29-labeled cells were predominantly localized in the terminal branches around the islets. The terminal branches also showed cells coexpressing islet hormones and cytokeratin 19.

CONCLUSIONS

The adult human pancreatic ducts showed islet hormone-producing cells. The insulin-reactive cells predominantly localized in terminal branches where they may retain potential capability for β-cell neogenesis.

CXCL14-Like Immunoreactivity Exists in Somatostatin-Containing Cells of Mouse Pancreas

Immunohistochemical techniques were employed to investigate the distribution of the chemokine CXCL14, in the mouse pancreas. CXCL14-immunoreactive cells were detected in the peripheral region of the pancreatic islets and were immunoreactive for somatostatin, but not for glucagon, insulin, and pancreatic polypeptide. Immunoelectron microscopy indicated that the CXCL14-like peptide and somatostatin co-existed in the secretory granules. CXCL14, secreted from somatostatin-containing cells, may modulate insulin secretion in a paracrine fashion, and play a novel role in glucose homeostasis in addition to its well-known chemotactic activities.

Principles of endocrinology

The endocrine system plays a major role in human survival. Endocrine glands secrete chemical messengers or hormones that affect every tissue of the body, including the periodontium, during the life of the individual. As the endocrine system influences a broad assortment of biological activities necessary for life, a general understanding of the principal components and functions of this system is essential. A fundamental assessment of hormone structure, mechanism of action and hormone transport, as well as influence on homeostasis is reviewed. A concise evaluation of the functions of the central endocrine glands, the functions of the major peripheral endocrine glands (other than gonadal tissues) and the known relationships of these hormones to the periodontium is examined.

Delineating potential control mechanisms of mammary protein synthesis utilizing atropine

Amino acids (AA) and/or somatotropin (ST) were infused into a jugular vein of lactating cows receiving atropine to determine the effect on milk protein secretion. Atropine decreased milk protein yield by 35%. Plasma alpha-amino nitrogen, which was decreased by 31% due to atropine, was restored to control levels upon AA infusion. Plasma ST concentration was not affected by atropine and, upon ST infusion, increased by 236% in treated animals. Amino acids, ST, or the combination of the two were unable to return milk protein to control levels in atropine-treated animals. Plasma insulin concentration decreased by 37% in atropine-treated animals and was not significantly different for cows receiving atropine as well as ST, AA, or both ST and AA. Similarly, glucagon decreased by 36% in atropine-treated animals but was partially restored in cows receiving AA. Overall, the insulin-to-glucagon ratio was not significantly affected by treatment. Plasma glucose concentration was not affected by treatment. These data lend support to the importance of the insulin-to-glucagon ratio in terms of whole-body metabolism, with the exception of the mammary glands, which are glucagon-insensitive and, therefore, sensitive to the observed decrease in circulating insulin concentration.