Monograph: |
Bile Acids and salts
The principal primary bile acids, cholic acid and
chenodeoxycholic acid , are produced in the liver from
cholesterol and are conjugated with glycine or taurine to give
glycocholic acid, taurocholic acid, glycochenodeoxycholic
acid. and taurochenodeoxycholic acid before being secreted
into the bile where they are present as the sodium or potassi-
um salts (bile salts). Secondary bile acids are formed in the
colon by bacterial deconjugation and 7a-dehydroxylalion of
cholic acid and chenodeoxycholic acid producing deoxychol-
ic acid and lithocholic acid respectively. Ursodeoxycholic
acid is a minor bile acid in man although it is the
principal bile acid in bears. Dehydrocholic acid is a
semisynthetic bile acid.
The total body pool of bile salts is abo-i 3 g, and most of the
secreted bile salts are reabsorbed in a process of enterohepatic
recycling, so that only a small fraction of this amount must be
synthesised de now each day.
Bile salts are strongly amphiphilic; with the aid of phosphol-
ipids they form micelles and emulsify cholesterol and other
lipids in bile. Oral administration of chenodeoxycholic acid
also reduces the synthesis of cholesterol in the liver, while
ursodeoxycholic acid reduces biliary cholesterol secretion ap-
parently by increasing conversion of cholesterol to other bile
acids. The bile acids (but not the bile salts) also have a chol-
erelic action, increasing the secretion of bile, when given by
mouth.
Chenodeoxycholic acid and ursodeoxycholic acid are given
by mouth in the management of cholesterol-rich gallstones
in patients unsuited to, or unwilling to undergo, sur-
gery. Ursodeoxycholic acid is also under investigation in
some liver disorders.
Preparations containing bile salts have been used to assist the
emulsification of fats and absorption of fat-soluble vitamins
in conditions in which there is a deficiency of bile in the gas-
tro-intestinal tract. Ox bile has also been used in the treatment
of chronic constipation.
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