Rhodamine 123 is a cationic dye that emits a green fluorescence. Research observations indicate that Rhodamine 123 can be used to probe the electrochemical gradient in mitochondria, in flow cytometry to detect the activity of P-glycoprotein efflux, and as a compound for P-GP mediating transport. Studies report that Rhodamine 123 can decrease the clonal growth of carcinoma cells in vitro, and that it can associate with placental P-gp. Rhodamine 123 is a substrate of Mdr (P-glycoprotein). Rhodamine 123 is a substrate of MRP1.