WordNet

(library science) the count of books that are loaned by a library over a specified period
movement through a circuit; especially the movement of blood through the heart and blood vessels
number of copies of a newspaper or magazine that are sold; "by increasing its circulation the newspaper hoped to increase its advertising"
the spread or transmission of something (as news or money) to a wider group or area
free movement or passage (as of cytoplasm within a cell or sap through a plant); "ocean circulation is an important part of global climate"; "a fan aids air circulation"
the dissemination of copies of periodicals (as newspapers or magazines)

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〈U〉『血液の循環』,血行 / 〈U〉(貨幣の)流通;(情報・うわさなどの)流布伝達;(新聞・雑誌など,印刷物の)配布 / 〈C〉(新聞・雑誌などの)発行部数

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出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2017/04/12 14:17:38」(JST)

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Enterohepatic circulation of drugs.

Enterohepatic circulation refers to the circulation of biliary acids, bilirubin, drugs, or other substances from the liver to the bile, followed by entry into the small intestine, absorption by the enterocyte and transport back to the liver.

Biliary acids

The circuit

Hepatocytes metabolize cholesterol to cholic acid and chenodeoxycholic acid. These lipid-soluble bile acids are conjugated (reversibly attached) mainly to glycine or taurine molecules to form water soluble primary conjugated bile acids, sometimes called "bile salts". These bile acids travel to the gall bladder during the interdigestive phase for storage and to the descending part of the duodenum via the common bile duct through the major duodenal papilla during digestion. 95% of the bile acids which are delivered to the duodenum will be recycled by the enterohepatic circulation.

Due to the pH of the small intestine, most of the bile acids are ionized and mostly occur as their sodium salts which are then called “primary conjugated bile salts.” In the lower small intestine and colon, bacteria dehydroxylate some of the primary bile salts to form secondary conjugated bile salts (which are still water-soluble). Along the proximal and distal ileum, these conjugated primary bile salts are reabsorbed actively into hepatic portal circulation. Bacteria deconjugate some of the primary and secondary conjugated bile salts back to lipid-soluble bile acids, which are passively absorbed into hepatic portal circulation. Finally, the conjugated bile acids which remained un-ionized conjugated bile acids are passively absorbed.

Venous blood from the ileum goes straight into the portal vein and then into the liver sinusoids. There, hepatocytes extract bile acids very efficiently, and little escapes the healthy liver into systemic circulation.

The net effect of enterohepatic recirculation is that each bile salt molecule is reused about 20 times, often multiple times during a single digestive phase.

Function

The presence of biliary acids in the intestines helps in digestion of fats and other substances.^[1]

Bilirubin

Bilirubin is conjugated with glucuronic acid in the liver by the enzyme glucuronyltransferase, making it soluble in water. Much of it goes into the bile and thus out into the small intestine. Although 95% of the secreted bile is reabsorbed by the small intestine, conjugated bilirubin is not reabsorbed in small intestine. All conjugated bilirubin in the large intestine is metabolised by colonic bacteria to urobilinogen, which is then further oxidized to urobilin and stercobilin. Urobilin, stercobilin and their degradation products give feces its brown color. ^[2] However, just like bile, some of the urobilinogen reabsorbed is resecreted in the bile which is also part of enterohepatic circulation. The rest of the reabsorbed urobilinogen is excreted in the urine where it is converted to an oxidized form, urobilin, which gives urine its characteristic yellow color.

Drugs

Enterohepatic circulation also means that some molecules which would not otherwise be very toxic can become of this recycling process.

References

^ Lipoproteins: Lipid Digestion & Transport by Joyce J. Diwan. Rensselaer Polytechnic Institute. Retrieved June 2012
^ Kuntz, Erwin (2008). Hepatology: Textbook and Atlas. Germany: Springer. p. 38. ISBN 978-3-540-76838-8.

External links

1040580666 at GPnotebook

UpToDate Contents

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1. ビリルビン代謝 bilirubin metabolism
2. 新生児における非抱合型高ビリルビン血症の発症機序および病因 pathogenesis and etiology of unconjugated hyperbilirubinemia in the newborn
3. 炎症性腸疾患の肝症状 hepatobiliary manifestations of inflammatory bowel disease
4. 非ステロイド性抗炎症剤（NSAIDs）：作用機序 nsaids mechanism of action
5. 栄養の吸収および吸収不良の機序 mechanisms of nutrient absorption and malabsorption

English Journal

Fibroblast growth factor-19 action in the brain reduces food intake and body weight and improves glucose tolerance in male rats.

Ryan KK, Kohli R, Gutierrez-Aguilar R, Gaitonde SG, Woods SC, Seeley RJ.SourceUniversity of Cincinnati, Metabolic Diseases Institute, 2170 East Galbraith Road, A-125, Cincinnati, Ohio 45237. karen.ryan@uc.edu.
Endocrinology.Endocrinology.2013 Jan;154(1):9-15. doi: 10.1210/en.2012-1891. Epub 2012 Nov 26.
Fibroblast growth factor-19 (FGF19) and its rodent ortholog, FGF15, are hormones produced in the distal small intestine and secreted into the circulation after a meal. In addition to controlling the enterohepatic circulation of bile acids, FGF15/19 also regulates systemic lipid and glucose metabolis
PMID 23183168

Altered enterohepatic circulation of bile acids in Crohn's disease and their clinical significance: a new perspective.

Nolan JD, Johnston IM, Walters JR.SourceDepartment of Gastroenterology, Imperial College NHS Trust, Hammersmith Hospital, Section of Hepatology & Gastroenterology, Imperial College, London, W12 0HS, UK.
Expert review of gastroenterology & hepatology.Expert Rev Gastroenterol Hepatol.2013 Jan;7(1):49-56. doi: 10.1586/egh.12.66.
The role of bile acids (BA) extends far beyond lipid digestion and cholesterol metabolism. The transcriptional regulation of multiple genes within the liver and intestine are under their influence. BA exert these effects through binding and activating receptors in much the same way as endocrine horm
PMID 23265149

Bile acid transporters and regulatory nuclear receptors in the liver and beyond.

Halilbasic E, Claudel T, Trauner M.SourceHans Popper Laboratory of Molecular Hepatology, Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Austria.
Journal of hepatology.J Hepatol.2013 Jan;58(1):155-68. doi: 10.1016/j.jhep.2012.08.002. Epub 2012 Aug 8.
Bile acid (BA) transporters are critical for maintenance of the enterohepatic BA circulation where BAs exert their multiple physiological functions including stimulation of bile flow, intestinal absorption of lipophilic nutrients, solubilization and excretion of cholesterol, as well as antimicrobial
PMID 22885388

Japanese Journal

Inhibitory Effect of Heat-Treated 3-(3′,4′-dihydroxyphenyl)-L-alanine (DOPA) on β-glucuronidase Activity

HASHIMOTO Kei,KINPARA Mika,UDA Yasushi
Food Science and Technology Research 19(6), 1115-1119, 2013
… A reduction in the activity of this enzyme could inhibit the enterohepatic circulation of carcinogens, which is thought to reduce the risk of colon cancer. …
NAID 130003392405

CJK-P-09 THE PHARMACOKINETICS OF RIFAMPICIN, CARBAMAZEPINE AND METFORMIN HYDROCHLORIDE IN MICE WITH CHOLECYSTECTOMY

Wei Y.H.,Wu X.A.,Zhang F.,Zhou Y.,Wang D.,Zhang G.Q.,Zhang J.P.
日本医療薬学会年会講演要旨集 22, 495, 2012-10-10
NAID 110009619420

Metabolic Acidosis during Treatment of Mushroom Poisoning: A Diagnostic Pitfall

Gatselis Nikolaos K.,Liamis George,Makaritsis Konstantinos P.,Dalekos George N.
Internal Medicine 51(9), 1077-1080, 2012
… Disruption of enterohepatic circulation with activated charcoal is a common practice for several intoxications, including mushroom poisoning. …
NAID 130002061788