Bile acids and salts of bile acids

BILE ACIDS AND SALTS OF BILE ACIDS


  • Bile salts are Na or K salts of glycocholic and tauro cholic acids formed in the liver and found in the bile.  In carnivores, man, sheep, goat and birds, tauro cholic acid predominate.  In pig and rabbit , it is the glyco cholic acid predominates.  Glycocholic acid is a compound of glycine (simplest amino acid), cholic acid (derived from cholesterol). Taurocholic acid is a compound of taurine (sulphur containing nitrogenous substance derived from an essential amino acid cystine) and cholic acid.  Chief bile acid is cholic acid.  Others are deoxycholic, lithocholic and chenodeoxy cholic acid .

Functions of bile salts

  • They have powerful surface tension reducing ability (Detergent effect) and thereby act as a strong emulsifying agent and assist in fat emulsification.  This allows the agitation in the intestinal tract to break the fat globules into minute sizes.
  • Activates pancreatic lipase.
  • Activates cholesterol esterases
  • They help in the absorption of fatty acids, monoglycerides, cholesterol and other lipids from the intestinal tract, by forming minute complexes of lipids which are called MICELLES .  These are highly soluble because of the electrical charges of the bile salts.  The lipids are “ferried” in this form to mucosa where they are absorbed. Without the bile salts about 40% of the lipids are lost into the stools.
  • Helps in absorption of fat soluble vitamins

Enterohepatic circulation 

  • Approximately 94% of the bile salts are reabsorbed by an active transport process through the intestinal mucosa in the dorsal ileum. 
  • On reaching the liver by portal circulation almost entire bile salts are absorbed by hepatocyte from venous sinusoids and recirculated into the bile so that these salts can circulate about 18 times before being voided in the feces.
  • Loss of bile salts  are replaced  by the liver.  This recirculation of the bile salts is called entero hepatic circulation. 
  • The amount of bile salt in the enterohepatic circulation alters the bile secretion.
Last modified: Saturday, 4 June 2011, 10:26 AM