[Tissue distribution of the multidrug-resistance gene product P-glycoprotein and its physiological function].

In normal tissues, P-glycoprotein(P-gp), which is expressed in various tumor cells, is found on the luminal surface of epithelia of the kidney proximal tubule, small intestine and colon and bile canalicular face of hepatocytes, as well as, in the adrenal and capillary endothelial cells in the brain and testis. The physiological function of P-gp remains unclear but growing amounts of information suggest that it can play a important role in the absorption from intestine, elimination from liver and kidney and distribution into brain across the blood-brain barrier for many cancer chemotherapeutic agents as well as other drugs which reverse multidrug resistance. The competition for the P-gp-mediated transports in tissues and organs, which express multidrug-transporter, might lead to unsuspected drug interactions among these drugs.