PMID: 8593279Jan 31, 1996Paper

Saturable P-glycoprotein kinetics assayed by fluorescence studies of drug efflux from suspended human KB8-5 cells

Biochimica Et Biophysica Acta
R I GhauharaliJ Lankelma

Abstract

This article describes a new and rapid method to determine the pumping rate of P-glycoprotein (P-gp) in intact cells. Multidrug resistant (MDR) human epidermoid carcinoma KB8-5 cells (containing P-gp) were loaded with daunorubicin (DNR) in the absence or in the presence of verapamil, sufficient to inhibit DNR pumping by P-gp. In either case, the cells were resuspended in medium devoid of DNR and the subsequent increase of the DNR fluorescence intensity was measured as a function of time. For cells loaded with the same amount of drug, the free cytosolic drug concentration (Ci(t)) was a unique function of the DNR medium concentration (Co(t)). The cellular drug content in the presence of verapamil decreased nonlinearly with decreasing extracellular drug concentration, indicating that the intracellular drug apparent distribution volume increased with decreasing cellular drug content. At each fluorescence intensity, we calculated the P-gp mediated (verapamil-inhibitable) DNR transport rate from the rate of increase of the DNR fluorescence intensity in the absence of verapamil minus the rate of increase of the DNR fluorescence intensity in the presence of verapamil. When plotted against the intracellular free drug concentration (as c...Continue Reading

References

Apr 1, 1992·International Journal of Cancer. Journal International Du Cancer·C H VersantvoortJ Lankelma
Jul 15, 1992·European Journal of Biochemistry·E C SpoelstraJ Lankelma
Dec 1, 1989·FASEB Journal : Official Publication of the Federation of American Societies for Experimental Biology·P F JurankaV Ling
Sep 19, 1989·Biochimica Et Biophysica Acta·J TarasiukL Gattegno
Jan 1, 1993·Annual Review of Biochemistry·M M Gottesman, I Pastan

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