Cell cycle-dependent Adriamycin uptake in Chinese hamster cells

Adriamycin fluorescence was measured by flow cytometry after exposing synchronized Chinese hamster (line CHO) cells to a fixed dose of adriamycin (ADR). Three synchrony methods were used: mitotic selection, isoleucine-deficient culture and pretreatment with low doses of ADR. Approximately a 1.6- to 2-fold increase in ADR fluorescence intensity was observed for cells in G2 + M compared to cells in G1. An increase in ADR fluorescence was also noted for cell populations exhibiting a G2 block after pretreatment with low-dose ADR. No significant difference in fluorescence intensity was observed for G1 cell populations with two different volume distributions. Results suggest that the magnitude of ADR fluorescence is affected by the cell cycle distribution and that cellular susceptibility to drug-induced cytokinetic changes during exposure must also be taken into consideration when measuring ADR uptake.