R406 stimulates ATPase activity in P-gp-enriched membranes.

The Corning Gentest ATPase assay was used to determine P-gp activity following treatment with R406. Membranes isolated from insect cells expressing P-gp were pre-incubated with R406 (1.0 to 10 μmol/L), verapamil (20 μmol/L) or docetaxel (1 μmol/L) for 5 min at 37 °C, followed by the addition of ATP and an additional 30 min incubation at 37 °C. A colorimetric reagent supplied by the manufacturer was added to each experimental condition and the plate was read at 800 nm. Conditions were run with and without sodium orthovanadate. All data are expressed as the average of triplicate measurements ± standard deviation.