Physiology, bile-acid enterohepatic circulation

Structure-Activity Reiationships for ASBT. The studies with endogenous bile acids have led to physiological understanding of the function of bile acids and the enterohepatic circulation. The search for a deeper understanding of the molecular mechanism behind the affinity and recognition of molecules by the bile acids carriers in both ileum and liver has led researchers to modify bile acids and study the carrier affinity of these compounds. These modifications typically entail either the substitution of the hydroxyl groups at the 3,7, or 12 positions by other functionalities or the... 

Under normal physiological conditions, bile acids undergo an enterohepatic circulation that involves only the liver and small intestine. 

Publication of a book devoted entirely to the chemistry, physiology, and metabolism of bile acids indicates a renascence in interest in these poly-functional detergents. Here we will summarize present views on the physical and physiological properties of bile acids in relation to their chemical structure which bear on their participation in the intestinal absorption of fat, their enterohepatic circulation, and their influence on electrolyte and water absorption by the colon. Several of these topics are considered in detail elsewhere in this book, as well as in recent reviews (1-4). This chapter will focus on our own studies but will also emphasize areas in which information is needed. 

Despite our increased knowledge of the synthesis, secretion and enterohepatic circulation of bile salts, several aspects of the effects of these sterol metabolites on the physiology of the intestine itself have not been emphasized and are poorly understood. This becomes of greater significance when we consider that bile acids, particularly chenodeoxycholic acid and ursodeoxycholic acids, are employed for gallstone therapy there are several dietary influences on the enterohepatic circulation of bile acids and on bile acid excretion (e.g. fats and dietary fibers) increased colonic bile acid concentrations have been implicated in the promotion of colorectal cancer and there appears to be an inverse relationship between cholesterolemia and colon cancer. 

Belknap. W.M. Balistreri, W.F., Suchy, F.J. and Miller, P. Physiologic cholestasis. II Serum bile acids reflect the development of the enterohepatic circulation in rats. Hepatology J. 613 (1981). 

The bile acid conjugates seem to have in. some way physiological importance in even part of this enterohepatic circulation (EHC). 

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