A kinetic study of Rhodamine123 pumping by P-glycoprotein

Yulin Wang, Da Cheng Hao, Wilfred D. Stein*, Ling Yang

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

41 Scopus citations

Abstract

The MDR1 P-glycoprotein (P-gp) actively extrudes a wide variety of structurally diverse cytotoxic compounds out of the cell, is widely expressed in the epithelial cells of kidney, liver and intestine, and in the endothelial cells of brain and placenta, and plays an important role in drug resistance. We measured the accumulation of Rhodamine 123 (Rho123), a substrate of P-gp, into a drug sensitive and a drug resistant strain of the human leukemia cell line K562, as function of Rho123 concentration. With the aid of a mathematical transformation, we used the accumulation of Rho123 into the sensitive cells as a surrogate measure for the internal concentration of the probe in the resistant cells, and were thus able to measure the kinetic parameters of drug efflux pumping by P-gp. Drug pumping was half-saturated at an external Rho123 concentration of 7.2E-06 ± 1.1E-06 M, and displayed a co-operative behaviour with a Hill number of 1.94 ± 0.32. Verapamil could be shown to inhibit Rho123 efflux uncompetitively.

Original languageEnglish
Pages (from-to)1671-1676
Number of pages6
JournalBiochimica et Biophysica Acta - Biomembranes
Volume1758
Issue number10
DOIs
StatePublished - Oct 2006

Keywords

  • Fluorescence
  • Kinetics
  • Pglycoprotein
  • Quenching
  • Resistance
  • Rhodamine 123

Fingerprint

Dive into the research topics of 'A kinetic study of Rhodamine123 pumping by P-glycoprotein'. Together they form a unique fingerprint.

Cite this