Activity of PGP, BCRP, MRP1 and MRP3. A.) Graph of mean fluorescence related to rhodamine-123 accumulation inside cancer cells obtained using FACS Aria II (Becton Dickinson, USA). Error bars refer to S.D. p < 0.05 was marked as *. One-way ANOVA followed by Tukey HSD post-hoc test was applied. B.) Representative overlay histograms of rhodamine-123 accumulation in CMT-U309 canine mammary cancer cells (control, markered as green), and treated with pgp -specific siRNA (markerd as red). The overlay histograms were created using Flowing Software (Turku University, Finland), http://www.flowingsoftware.com.