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Relation among the resistance factor, kinetics of uptake, and kinetics of the P-glycoprotein-mediated efflux of doxorubicin, daunorubicin, 8-(S)-fluoroidarubicin, and idarubicin in multidrug-resistant K562 cells
United States: American Society for Pharmacology and Experimental Therapeutics
Erscheinungsjahr
1996
Quelle
MEDLINE
Beschreibungen/Notizen
Multidrug resistance (MDR) is frequently associated with decreased cellular drug accumulation resulting from enhanced drug
efflux. This is correlated with the presence of a membrane protein, the P-glycoprotein, which pumps a wide variety of drugs
out of cells, reducing their intracellular concentration and thus their toxicity. The influx and efflux of drugs across the
cell membrane are in large part responsible for their intracellular concentrations, and in the search for new compounds able
to overcome MDR, it is of prime importance to determine the molecular parameters whose modification would lead to an increase
in the kinetics of uptake and/or to a decrease in the P-glycoprotein-medicated efflux. Four anthracycline derivatives, doxorubicin,
daunorubicin, 8-(S)-fluoroidarubicin, and idarubicin, which have the same amino sugar, were used to analyze the respective
contribution of the kinetics of uptake and the P-glycoprotein-mediated efflux in their impaired accumulation in MDR cells.
The kinetics of uptake of the four drugs vary over a very large range: the kinetics of uptake of daunorubicin, 8-(S)-fluoroidarubicin,
and idarubicin are 16, 200, and 400 times higher than that of doxorubicin, respectively. However, the four drugs are extruded
by P-glycoprotein at comparable rates. The apparent Km values for P-glycoprotein-mediated transport, the intracellular free
cytosolic drug concentrations at half-maximal velocity for the cell lines used, were approximately 2.2 microM for daunorubicin
and and approximately 1 microM for idarubicin and 8-(S)-fluoroidarubicin.