Multidrug Resistance : The Role Of The ATP-Binding Cassette Superfamily Transport Protein, P-Glycoprotein
Multidrug resistance is a condition in which cells exhibit resistance to drugs to which they have never been exposed to previously. The main factor contributing to this is the overexpression of an energy-dependant multidrug transporter, P-glycoprotein. P-glycoprotein is also involved in the normal physiological functions. P-glycoprotein is widely distributed in the body and found in organs like lower gastrointestinal tract, kidney, liver, pancreas, testes and most importantly, the blood-brain barrier. Although, many mechanisms have been promulgated which involve P-glycoprotein in multidrug resistance, there is no satisfactory mechanism that reconciles the entire phenomenon related to multidrug resistance. Efforts have also been taken to isolate, characterize and spectroscopically analyze P-glycoprotein. Based on the available data, there are many agents, which are proven to be the substrates of P-glycoprotein. Moreover, there also are inhibitors to Pglycoprotein that enhance the intracellular levels of many drugs that are effluxed by P-glycoprotein.