A pancreatic islet cell is found in the pancreas inside what are known as the islets of Langerhans. The pancreas is an organ in the digestive system which produces digestive enzymes and hormones. Most of the pancreas consists of enzyme-producing cells, with the hormone-producing islets of Langerhans scattered throughout like islands in the sea. Each islet of Langerhans consists of a number of different types of pancreatic islet cell. The main pancreatic islet cell types are known as alpha, beta and delta, or A, B and D, and these secrete the hormones glucagon, insulin and somatostatin, respectively.
Only about two percent of the pancreas is taken up by the islets of Langerhans, while enzyme-producing cells occupy about 80 percent of the gland. Inside each islet of Langerhans, the different pancreatic islet cells are arranged so that the B cells are in the center, surrounded by A and D cells. Every islet has an excellent blood supply, enabling hormones to be released quickly into the circulation.
Each type A pancreatic islet cell produces glucagon, a hormone which stimulates the release of glucose from body stores into the blood. The type B pancreatic islet cell has an opposite effect, as it secretes insulin, which causes increased storage of glucose. Somatostatin, the hormone produced by the type D pancreatic islet cell, helps to regulate hormone secretion from the islets.
The most common cell in each islet of Langerhans is the B cell. B cells may account for up to three-quarters of all the cells present. Sometimes the immune system attacks B cells and destroys them so that insulin is no longer produced by the pancreas. This results in the disease known as type 1 diabetes mellitus, where patients have to inject insulin for life. Untreated type 1 diabetes results in weakness and excessive thirst and urination, which could lead to dehydration, coma and death.
It is thought that islet transplantation, where islets of Langerhans are removed from donor pancreases and implanted into the liver of a type 1 diabetes patient, could provide a future treatment for the disease. Research has already shown that islet transplantation can allow patients to live without daily insulin injections for a limited period of time. Other people have been able to reduce their daily insulin requirement. As it is an experimental procedure, transplantation is normally reserved for patients who have diabetes which is difficult to control.
