<?xml version='1.0' encoding='UTF-8'?><xml><records><record><source-app name="HighWire" version="7.x">Drupal-HighWire</source-app><ref-type name="Journal Article">17</ref-type><contributors><authors><author><style face="normal" font="default" size="100%">WESOŁOWSKA, OLGA</style></author><author><style face="normal" font="default" size="100%">MOLNAR, JOSEPH</style></author><author><style face="normal" font="default" size="100%">OCSOVSZKI, IMRE</style></author><author><style face="normal" font="default" size="100%">MICHALAK, KRYSTYNA</style></author></authors><secondary-authors></secondary-authors></contributors><titles><title><style face="normal" font="default" size="100%">Differential Effect of Phenothiazines on MRP1 and P-Glycoprotein Activity</style></title><secondary-title><style face="normal" font="default" size="100%">In Vivo</style></secondary-title></titles><dates><year><style  face="normal" font="default" size="100%">2009</style></year><pub-dates><date><style  face="normal" font="default" size="100%">2009-11-01 00:00:00</style></date></pub-dates></dates><pages><style  face="normal" font="default" size="100%">943-947</style></pages><volume><style face="normal" font="default" size="100%">23</style></volume><issue><style face="normal" font="default" size="100%">6</style></issue><abstract><style  face="normal" font="default" size="100%">Background: Overexpression of ATP-binding cassette (ABC) transporters such as P-glycoprotein (P-gp), multidrug resistance-associated protein 1 (MRP1) or breast cancer resistance protein (BCRP) accounts for majority of cases of multidrug resistance (MDR) of cancer cells. Materials and Methods: In the present work, the interactions of seven commercially available phenothiazine derivatives, known P-glycoprotein inhibitors, with this transporter and MRP1 were compared. By flow cytometry, it was shown that all the drugs increased the accumulation of rhodamine 123 in the P-gp-overexpressing lymphoma cell line L5178 MDR. On the other hand, phenothiazine derivatives stimulated MRP1-mediated efflux of fluorescent probe (BCPCF) out of human erythrocytes. Results: In this way, these phenothiazine derivatives were identified as a group of atypical MDR modulators that differently interact with P-gp (as inhibitors) and MRP1 (as stimulators). Conclusion: This observation clearly shows that the activity of all new modulators should be tested for their effects towards different ABC transporters as a standard procedure.</style></abstract></record></records></xml>