ABC Transporters in Intestinal and Liver Efflux

The ABC superfamily of transporters consists of 51 human genes in 7 subfamilies. The ABC transporters involved in drug transport are found in many tissues in the body including the liver, kidney, brain, and intestine. The liver and the intestine are the tissues most important in the oral bioavailability of drugs. This chapter focuses on the ABC efflux transporters present in liver and intestine and their roles in the oral bioavailability and hepatobiliary excretion of xenobiotics. It discusses factors that affect the expression and function of efflux transporters in the liver and intestine. ABCB11 is a monovalent bile salt efflux protein located predominantly on the canalicular membrane in liver hepatocytes. Excretion of bile salts from liver hepatocytes into bile canaliculi is a major driving force for bile flow and can be a rate-limiting step. The ABC family of efflux transporters are determinants of the absorption and disposition of substrates for the transporters.