The endocrine function of pancreas is based on the diffusely spread islets of Langerhans, which include endocrine cell types that secrete insulin and other hormones. An analysis of the genes with elevated expression in pancreas reveals that the corresponding proteins are expressed in the various cell types present in pancreas.
Proteins specifically expressed in islet cells of pancreas
The islet cells constitute 2% of the pancreas, and are responsible for maintaining a steady blood glucose level by secreting hormones regulating uptake and release of glucose.Examples of proteins expressed in islet cells include INS, which is secreted following elevated blood glucose levels and stimulates glucose uptake upon binding insulin receptor, and, GCG, which elicits an opposite effect by raising blood glucose levels. Another important protein is IAPP, a hormone that regulates glucose metabolism and act as a satiation signal.
Pancreas histology
The exocrine component is composed of lobular units of acini, which discharge their secretions into progressively larger ducts that finally merge into the main pancreatic duct, which ends in duodenum. The pyramidal-shaped acinar cells are filled with eosinophilic zymogen granules.The islets of Langerhans, which constitute 1-2% of the cell mass in the adult pancreas, represent the endocrine component of the pancreas. The islets are round, compact structures that are highly vascularized with sparse connective tissue.
The main cell types in the islets are beta cells - responsible for insulin production, alpha cells - responsible for glucagon secretion, delta cells - responsible for somatostatin secretion and PP cells - the pancreatic polypeptide secreting cells. The histology of human pancreas including detailed images and information about the different cell types can be viewed in the Protein Atlas Histology Dictionary.