Acinar cells are cells of the exocrine pancreas that synthesize, store, and secrete digestive enzymes. They produce almost all of the enzymes needed for digestion in the small intestine, including endo- and exo-proteases, nucleases, lipases and glycosidases. The rate of protein synthesis in acinar cells is higher than any other cell in the adult body, and they are highly adapted for this function.
What is an acinar cell?
Acinar cells are specialized cells of the exocrine pancreas whose function is to produce, secrete, and store digestive enzymes. The name ‘acinar’ (from the Latin word ‘acinus’, which means ‘berry’) refers to the arrangement of these cells in the pancreas, where they are grouped in bunches of grapes called acini. The acini secrete all of the enzymes needed to digest carbohydrates, proteins, and lipids in the small intestine.
Function of the exocrine pancreas
The main function of the pancreas is to produce enzymes for digesting food molecules. Around 95% of the pancreas is made up of exocrine tissue, which contains acinar cells and secretes digestive enzymes. The rest of the pancreas is there endocrine tissue, which is made up of endocrine cells called islets of Langerhans. The main function of the endocrine pancreas is to control blood sugar levels by releasing hormones such as insulin into the bloodstream.
Structure and function of acinar cells
Acini in the pancreas are made up of groups of acinar cells that synthesize and secrete enzymes that help digest dietary carbohydrates, proteins, and lipids. Acinar cells are highly adapted to the production, storage, and secretion of digestive enzymes.
Pancreatic acinar cells produce almost all of the enzymes needed to digest food in the small intestine, including endo- and exoproteases, nucleases, lipases, and glycosidases. Therefore, they synthesize proteins at a very high speed; In fact, they produce and secrete more proteins than any other cell in the adult body. Acinar cells are specially adapted for this function and contain abundant rough endoplasmic reticulum (RER) for protein production and processing.
Over 90% of the proteins produced in acinar cells are packaged in specialized organelles known as Zymogen granules. Digestive enzymes are stored in the zymogen granules until needed, after which they are exocytosed by the acinar cells.
Zymogen granules have an acidic pH level that inhibits the activity of digestive enzymes and helps prevent possible digestion of pancreatic tissue. Enzymes can also be stored in an inactive form to minimize the risk of damage to the pancreas.
Enzymes are stored in the zymogen granules of acinar cells until they are needed for digestion. The contents of the zymogen granules are released by exocytosis and travel through the pancreatic duct to the duodenum (i.e., the first section) of the small intestine. Digestive enzymes are usually not activated until they reach the duodenum.
Acinar cells and acute pancreatitis
Acinar cells are associated with acute pancreatitis; a condition in which the pancreas becomes painfully inflamed. Gallstones are the most common cause of acute pancreatitis. They block the ducts that connect the pancreas to the gallbladder, which leads to a build-up of enzymes in the pancreas. The enzymes then begin to digest the pancreatic tissue and cause severe inflammation.
Acute pancreatitis is most commonly associated with gallstones and / or excessive alcohol consumption. However, studies suggest that acinar cells can play a key role in the onset of the disease. In healthy people, digestive enzymes are not activated until they reach the duodenum of the small intestine. Premature activation of these enzymes within the acinar cells leads to the development of pancreatitis and inflammation of the surrounding tissues.