Kinetic parameters for the uptake of anthracycline by drug-resistant and drug-sensitive K562 cells.

Fluorescence-emission spectra from anthracycline-treated cells suspended in buffer have been used to measure the uptake of three anthracycline derivatives: adriamycin, 4'-O-tetrahydropyranyladriamycin and aclacinomycin in drug-sensitive and drug-resistant K562 cells. The initial rate of uptake and the kinetics of active efflux under the effect of an integral membrane glycoprotein, P-glycoprotein, have been measured as a function of temperature. The activation energies for the passage of the drugs through the plasma membrane have been calculated. In the case of 4'-O-tetrahydropyranyladriamycin, the activation energies for the passive diffusion of the drug equal 45 kJ.mol-1 and 37 kJ.mol-1 for sensitive and resistant cells, respectively. The activation energy for the active efflux of 4'-O-tetrahydropyranyladriamycin equal 25 kJ.mol-1.