Effect of chloroquine on cellular daunorubicin distribution. U-A10 cells were exposed to chloroquine (0 to 100 μmol/L) for 2 hours before the addition of daunorubicin to a final concentration of 500 ng/mL for 1 hour. The cells were then washed, visualized by fluorescence microscopy, and photographed. Shown are photographs of typical single cells (with images centered within the frame) after treatment with 10 μmol/L chloroquine (A and B) or 100 μmol/L chloroquine (C and D) before daunorubicin exposure.