Cholecystokinin

Three molecular forms of cholecystokinin were revealed in the mucous membrane of the small intestine, which differ in the number of amino acid residues (cholecystokinin-8, cholecystokinin-12 and cholecystokinin-ZZ). Cholecystokinin-8 accounts for 60-70%. ^[2]

There are a number of other forms of cholecystokinin: cholecystokinin-58 (abbreviated name CCK58), cholecystokinin-58-disonopeptide ((1-49) -CCK58), cholecystokinin-Z9 (CCK39), cholecystokinin-25 (CCK25), cholecystokinin-18 (CCK18) ), cholecystokinin-7 (CCK7), cholecystokinin-5 (CCK5), ^[3] CCK-4 .

The amino acid sequence of cholecystokinin-33: H-Lys-Ala-Pro-Ser-Gly-Arg-Val-Ser-Met-lle-Lys-Asn-Leu-GIn-Ser-Leu-Asp-Pro-Ser-His-Arg- lle-Ser-Asp-Arg-Asp-Tyr-Met-Gly-Trp-Met-Asp-Phe-OH. ^[four]

Cholecystokinin acts as a mediator in a variety of processes occurring in the body, including digestion. In addition, cholecystokinin acts as a regulator of behavioral physiological acts. It has antidepressant properties. It is related to the emotions of fear and the pathogenesis of schizophrenia . ^[4] Influences a person’s nutritional behavior, causing a feeling of satiety and controlling appetite .

Low molecular forms of cholecystokinin are inactivated during the first passage through the liver , while large molecular cholecystokinin enters the systemic circulation from the liver. The concentration of cholecystokinin in the blood of a healthy person is 5-800 ng / l. ^[5] Through the bloodstream, cholecystokinin can pass through the kidneys into the urine , while maintaining biological activity (urocholecystokinin). ^[2]

The role of cholecystokinin in digestion

In the organs of the gastrointestinal tract, cholecystokinin is produced by I-cells of the duodenum and jejunum. In addition, cholecystokinin is found in pancreatic islets and various intestinal neurons. Cholecystokinin secretion stimulants are proteins , fats , especially those with a long chain of fatty acids (fried foods), components of choleretic herbs ( alkaloids , protopin , sanguinarine , essential oils , etc.), and acids ( but not carbohydrates ). A gastrin-releasing peptide is also a stimulant for cholecystokinin release.

Cholecystokinin stimulates the relaxation of the sphincter of Oddi ; increases the flow of hepatic bile; increases pancreatic secretion; reduces the pressure in the biliary system: it causes a reduction in the pylorus , which inhibits the movement of digested food into the duodenum. ^{[6] [5]} Cholecystokinin is a blocker of hydrochloric acid secretion by the parietal cells of the stomach. ^[7]

An inhibitor of cholecystokinin is somatostatin .

Cholecystokinin is used as a stimulant in a manometric study of the Oddi sphincter . In healthy patients, the consequence of its administration should be a decrease in the frequency and amplitude of the phase pressure waves, as well as the basal pressure of the sphincter of Oddi. A different reaction to the cholecystokinin test is a sign of sphincter of Oddi dysfunction . ^[eight]

E.K. Ivy and E. Oldberg (E. Oldberg) in 1928 discovered a regulatory peptide in the mucosal extract that causes contraction of the gallbladder and the release of bile into the duodenum, ^[9] which was named “ cholecystokinin "(from Greek choly - bile, kýstis - bubble and kieō - to move). A. A. Harper and A. S. Harper in 1943 isolated a peptide capable of stimulating pancreatic secretion from the mucous membrane of the small intestine and called it “pancreosimine” for this ability. ^[10] In the 1960s, the identity of cholecystokinin and pancreosimine was established. ^[eleven]