Identification of a multidrug resistance-like system in Tetrahymena pyriformis: evidence for a new detoxication mechanism in freshwater ciliates

The freshwater ciliate Tetrahymena pyriformis is an ubiquitous organism tha t is present in all aquatic ecosystems, This protozoan shelved a clear resi stance against some polycyclic aromatic hydrocarbons which can be attribute d to an efflux pump probably of the multidrug resistance (MDR) type. Immuno cytochemical detection showed a positive stain of ciliate cells Ising the m onoclonal antibodies 4E3, raised against P-glycoprotein (P-gp), The kinetic s of P-gp expression were studied for control cultures and cultures treated with 15 mu M benzo(a)pyrene, Western blot analysis using the Ab1, anti-P-g p polyclonal antibodies indicates the presence of two bands of 66 and 96 kD a of which the intensity increased with time in benzo(a)pyrene-treated cili ates, Uptake experiments with target compounds for the MDR pump, namely adr iamycin, rhodamine 123 and two polycyclic aromatic hydrocarbons, benzo(a)py rene and 7,12-dimethylbenzanthracene, were carried out by flow cytometry, i n the presence or absence of cyclosporin (an inhibitor of the multidrug res istant pump), The data indicate that the accumulation of these compounds by ciliate cells is significantly enhanced in the presence of cyclosporin, Th is suggests that Tetrahymena is provided with a P-gp-like system that is fu nctionally active in a way similar to that of the mammalian P-gp. (C) 1999 Federation of European Biochemical Societies.