In addition to conferring MDR in tumor cells, ABC transporters are also expressed in the membranes of healthy cells, where they facilitate the transport of various endogenous substances, as well as of substances foreign to the body.
Pored uzrokovanja MDR kod tumorskih ćelija, ABC transporteri su takođe izraženi u membranama zdravih ćelija, gde posreduju transport raznih endogenih supstanci, kao i niza supstanci koje su strane telu.