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KMID : 0381219750070060353
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Journal of RIMSK
1975 Volume.7 No. 6 p.353 ~ p.364
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Bile Salts and Liver
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Hong Sa-Suk
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Abstract
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Attempt is made in this paper to summarize present knowledge cf the physiology of bile acids and their relation to cholesterol gallstones. Bile is continuously secreted at variable rates by polygonal cells of the liver into bile canaliculi, from which it flows into the hepatic duct.
In man, the rate of bile secretion ranges from 250 to 1, 100 ml per day and is under nervous, humoral and chemical control. Bile salts themselves are powerful choleretics. In animals having gallbladder, the sphincter at the duodenal termination of bile duct is clcsed in the interdigestive period, with the result that bile is diverted into gallbladder, where bile salts and pigments are concentrated by rapid reabsorption of water and electrolytes. Within several minutes after meal, the gallbladder discharges its content into the intestinal lumen, where most of bile acids pool reabsorbed and circulates through the enterohepatic circulaticn at least twice during each meal and only small amount of bile acids are excreted into feces. The formation of bile acids is the major pathway for the metabolism and excretion cf chclesterol in mammals. Man synthesizes only two primary bile acids (cholic and chenodeoxychc,:c acid; and conjugate each of these with either glycine or taurine, approximately 3 : 1 proportion ratio). The initial step to form bile acids from cholesterol is 7a-hydroxylation which is major locus for feedback regulation of bile acids biosynthesis. Biliary drainage is knwcn to have profound effects on the rate of bile acids synthesis. In the intestines, microorganisms transform some of bile salts into secondary bile acids, such as deoxycholic and lithochclic acid. Bile acids have physicochemical properties similar to those of detergents in that they are amph_paths. Conjugated bile acids are very soluble in water and above a certain concentration individual bile acid molecules aggregate to form macromolecular complexes known as micelles. The solubilization of biliary cholesterol and lecithin in aquous bile is achieved by the formation of mixed micelles with bile salts.
Recently, a triangular diagram depicting the interrelationship of the three biliary lipid components by plotting the molar percentage of bile salts, cholesterol and lecithin, and a numerical expression of cholesterol saturation index were devised. In these manner each bile sample can be distinguished whether it is lithogenic or not. Bile salts also have stimulatory effect on biliary lipid secretion. In a recent study it was reported that the cholesterol gallstone was dissolved by longterm administration of chenodeoxycholic acid. But the present status of chencdecxychclic acid treatment must be considered investigative and any assessment regarding its eventual therapeutic role is premature at this time.
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