Colecistochinina

Colecistochinina, known in English as cholecystokinin (CCK), is a peptide hormone and neuropeptide produced in the gastrointestinal tract and brain. In humans, the major source is the enteroendocrine I cells of the duodenal and jejunal mucosa, although it is also expressed in certain brain regions. It is synthesized as part of a larger precursor, preprocholecystokinin, which is processed to yield several active peptides, including CCK-58, CCK-33, CCK-22, and the prevalent circulating form CCK-8. All active forms share a common C-terminal region essential for receptor activation.

Release of colecistochinina is triggered when chyme entering the small intestine contains fat or protein. In response, the intestinal mucosa secretes CCK into the circulation, where it can act locally and systemically.

Physiological actions of colecistochinina include stimulation of gallbladder contraction and bile release, stimulation of pancreatic enzyme secretion, and slowing of gastric emptying. It also relaxes the sphincter of Oddi to facilitate the flow of bile and pancreatic juice into the duodenum. In addition to its digestive role, colecistochinina functions as a brain neuropeptide involved in satiety, modulation of anxiety, and aspects of memory.

Receptors and distribution: CCK exerts its effects primarily through two receptor families, CCK1 (CCK-A) and CCK2 (CCK-B). CCK1 receptors are mainly associated with gallbladder and pancreatic responses, while CCK2 receptors are widely expressed in brain and gut and respond to both cholecystokinin and gastrin.

Clinical relevance: CCK signaling has been a focus of research in obesity and anxiety, and pharmacological agents targeting CCK receptors are studied for various conditions. Diagnostic use includes CCK-cholescintigraphy to assess gallbladder function by measuring ejection fraction after exogenous CCK administration.