Influences of glutathione on anionic substrate efflux in tumour cells expressing the multidrug resistance-associated protein, MRP111Abbreviations: BCECF, 2′,7′-bis-(2-carboxyethel)-5-(and-6)-carboxyfluorescein; BCECF-AM, 2′,7′-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein acetoxymethyl ester; BSO, buthionine sulfoximine; calcein-AM, calcein acetoxymethyl ester; CMFDA, chloromethylfluorescein diacetate; DNP-SG, dinitrophenyl-S-glutathione; GS-MF, methylfluorescein-glutathione; MRP1, multidrug resistance-associated protein; and LTC4, leukotriene C4.