title: Enhanced efflux of [3H]vinblastine from Chinese hamster ovary cells transfected with a full-length complementary DNA clone for the mdr1 gene.
abstract: Multidrug-resistant Chinese hamster ovary cell clones stably transfected with, and overexpressing, the mouse mdr1 complementary DNA clone along with drug-sensitive Chinese hamster ovary control cells were characterized for their capacities to accumulate and retain [3H]vinblastine. Multidrug-resistant mdr1 transfectants show a 3-4-fold decrease in [3H]vinblastine accumulation, compared to their drug-sensitive counterparts. After ATP depletion, this difference in [3H]vinblastine accumulation between mdr1 transfectants and control cells effectively disappears. This ATP-dependent decreased drug accumulation is paralleled in mdr1 transfectants by an enhanced capacity of these cells to extrude the drug in an ATP-dependent manner. In medium containing glucose and glutamine, the mdr1 transfectants release preloaded drug at a rate five times that of control, drug-sensitive cells. In ATP-depleted control and mdr1-transfected cells, there is little difference in the rate or extent of [3H]vinblastine release. The observation that the mdr1 transfectants show a decreased [3H]vinblastine accumulation and an increased vinblastine release, both of which are abolished when cellular ATP levels are reduced, provides a direct demonstration that the product of the transfected mdr1 gene is responsible for a mechanism controlling cellular drug levels in an ATP-dependent manner. However, attempts to establish competition for [3H]vinblastine transport by vincristine, daunomycin, and actinomycin D were only partly successful in mdr1 transfectants.
authors.affiliation: Department of Biochemistry, McGill University, Montreal, Canada.
authors.forename: J R
authors.initials: JR
authors.lastname: Hammond
authors.forename: R M
authors.initials: RM
authors.lastname: Johnstone
authors.forename: P
authors.initials: P
authors.lastname: Gros
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D002460:Cell Line; D006224:Cricetinae; D003412:Cricetulus; D004247:DNA / Q000235:genetics*; D004351:Drug Resistance / Q000235:genetics*; D005260:Female; D007700:Kinetics; D010053:Ovary; D010957:Plasmids; D014162:Transfection; D014316:Tritium; D014747:Vinblastine / Q000378:metabolism*
chemical_list: D000970:Antineoplastic Agents; D014316:Tritium; D014747:Vinblastine; D000255:Adenosine Triphosphate; D004247:DNA