Involvement of vacuolar H(+)-adenosine triphosphatase activity in multidrug resistance in HL60 cells.
HL60 cells isolated for resistance to vincristine (HL60/Vinc cells) or doxorubicin (HL60/Adr cells) contain enhanced levels of an energy-dependent drug efflux pump. HL60/Vinc cells contain the drug transporter P-glycoprotein, whereas the HL60/Adr isolate does not. In the present study, we examined the possible involvement of vacuolar H(+)-adenosine triphosphatase (H(+)-ATPase) activity in drug resistance in HL60 cells. We utilized bafilomycin A1, an agent which selectively inhibits vacuolar H(+)-ATPase activity at low concentrations. The results showed that bafilomycin A1 induced a major increase in drug accumulation and inhibited drug efflux in both HL60/Adr cells and HL60/Vinc cells. Similar results were obtained with 7-chloro-4-nitrobenz-2-oxa 1,3 diazole, an agent which is also capable of inhibiting vacuolar H(+)-ATPase. Azide, an inhibitor of F1F0 mitochondrial ATPase, and vanadate and ouabain, which are inhibitors of E1E2-type ATPase, did not affect drug levels in resistant cells. We also observed that bafilomycin A1 did not compete with [3H]azidopine binding to P-glycoprotein. Thus, bafilomycin A1 does not appear to function as a substrate for P-glycoprotein. These results suggest an involvement of vacuolar H(+)-ATPase activity in the pathway of drug efflux from HL60/Adr cells and HL60/Vinc cells. The mechanism of this action remains to be determined.
Marquardt
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Division of Biology, Kansas State University, Manhattan 66506.
Center
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D000900:Anti-Bacterial Agents / Q000494:pharmacology; D003630:Daunorubicin / Q000493:pharmacokinetics; D004317:Doxorubicin / Q000494:pharmacology; D004351:Drug Resistance / Q000502:physiology; D006801:Humans; D007942:Leukemia, Experimental / Q000201:enzymology* / Q000378:metabolism; D007951:Leukemia, Myeloid / Q000201:enzymology* / Q000378:metabolism; D018942:Macrolides; D006180:Proton-Translocating ATPases / Q000037:antagonists & inhibitors / Q000502:physiology*; D014316:Tritium; D014407:Tumor Cells, Cultured; D014617:Vacuoles / Q000201:enzymology*; D014750:Vincristine / Q000494:pharmacology
D000900:Anti-Bacterial Agents; D018942:Macrolides; D014316:Tritium; D014750:Vincristine; D004317:Doxorubicin; C040929:bafilomycin A1; D006180:Proton-Translocating ATPases; D003630:Daunorubicin