Fig. 1.

The P-gp substrate dLop is trapped in lysosomes. (A) Reduction of [³H]dLop (1 nM) accumulation in control KB-3–1 cells by compounds that increase lysosomal pH (i.e., lysosomotropic agents). Data represent mean ± SD (n = 3 observations); error bars are unidirectional for figure clarity. (B) The effect of temperature on the accumulation of [³H]dLop (1 nM) in control (KB-3-1) and P-gp–expressing (KB-8-5-11) cells. Accumulation in control (□) cells is much lower at 4 °C than at 37 °C, and accumulation in P-gp–expressing (■) cells is not affected by temperature (***P < 0.001). Data represent mean ± SD (n = 3 observations).