Biotransformation, Elimination and Bile Acid Metabolism

Abstract

The liver detoxifies and excretes both exogenous xenobiotics, such as drugs and environmental toxins, and endogenous substances, including ammonia and bilirubin. Efficient processing and elimination of these substances prevent cellular injury, including CNS toxicity in the case of ammonia and bilirubin. Hepatic synthesis, secretion and re-uptake of bile acids is an exquisitely regulated process that allows modulation of cholesterol metabolism and efficient absorption of the products of fat digestion, as well as compensatory trafficking of bile acids out of the hepatocyte in the face of bile acid retention as occurs in cholestasis. Nuclear receptor transcription factors tightly regulate these processes and offer potential therapeutic targets for new approaches to treatment of a variety of diseases. This chapter reviews these important functions of the liver, underscoring another aspect of its central role in human physiology.