Fig. 2.

Intracellular doxorubicin concentration in cells incubated at physiological and low ambient pH. Overlay of transmission picture of cells and nuclei shows that most of the doxorubicin (green) is retained in the nucleus (a). The doxorubicin retention was significantly higher at pH 7.2 than at low pH, and co-incubation with 10 μM verapamil significantly increased the doxorubicin retention at lower pH (b). c Mean intensity from 35 nuclei in the various groups. d Despite significantly higher intracellular doxorubicin concentration, upon co-incubation with 10 μM verapamil along with 2 μM doxorubicin did not affect cell survival. Results are ± SEM. *Significant high amount of doxorubicin in the nuclei of cells connected via horizontal line: *<0.01 and ***<0.001