Gastrointestinal absorption bile acid transporter

I he average daily intake of total dietary cholesterol is 400-500 mg. Cholesterol also enters the gastrointestinal tract via the bile. Between fiOO and 1200 mg of free cholesterol is secreted in the bile per day. By weight, bile consists of 92% water, 6% bile salts, 0,3% cholesterol, and small amounts of bilirubin, fatty acids, phosphatidylcholine, and sails. The cholesteryl esters of the diet are hydmlyzed to free cholesterol and a fatty add by pancreatic cholesterol esterase. After entry into the enterocyte, the free cholesterol is nmverted back to cholesteryl esters by acyl CoA cholesterol acyl transferase. Some evidence suggests that the absorption of dietary cholesterol (from the bile salt micelles) is mediated by a membrane-bound transport protein of the brush border (1 humhofer and Hauser, 1990),... 

The rate of vitamin K absorption in humans depends on the kind of fats included in the diet. Long-chain unsaturated fatty acids facilitate absorption of vitamin Kj in lymphatic vessels. The efficiency of this process is affected by the presence of bile salt and pancreatic juices, the form of vitamin K, as well as the site in the gastrointestinal tract. Vitamin Kj is primarily absorbed in the jejunum and ileum only small amounts are absorbed in the colon. From the lymphatic system, vitamin K is transported to the circulatory system and, in chylomicrons, to the liver from which it is distributed to target tissues. 

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