QS Study

Enterohepatic Circulation of Bile Salts

Bile is a secretory product of liver made up of salt, pigment and other substances, dissolved in an alkaline solution which is stored in Gallbladder. Bile salts are a component of bile, a fluid secreted from the gallbladder during the digestion of lipids. The function of bile salts in the duodenum is to solubilize ingested fat and fat-soluble vitamins, facilitating their digestion and absorption.

Enterohepatic circulation is an especially important concept in the field of toxicology as many lipophilic xenobiotics undergo this process causing repeated liver damage. It allows for recycling of metabolized and non-metabolized compounds and is of critical importance in toxicologic processes involving the gastrointestinal tract. About 90 – 95% (Away 9%) of the bile salts are reabsorbed into the blood from the small intestine, about one half of this by diffusion through the mucosa in the early portion of the small intestine and the remainder by an active transport process through the intestinal mucosa in the distal ileum. They then enter the portal blood and pass back to the liver. On reaching the liver, on first passage through the venous sinusoids, these salts are absorbed almost entirely into the hepatic cells and then are resecreted into the bile. This recirculation to the bile salts is called the enterohepatic circulation. It 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. The total bile salt is a pool of approximately 3.5 gram recycles repeatedly via the enterohepatic circulation.

Fig: Enterohepatic circulation of bile salts