Influence of inhibitors on the SP profile of A549 cells.

A549 cells were stained with Hoechst 33342, allowed to efflux, and then analyzed by flow cytometry for red/blue staining characteristics. The conditions for staining and efflux were designed for (A) maximal efflux (ie, no inhibitors), (B) ATP depletion, or (C-F) inhibition by pump-specific drugs.