EFFECTS OF PENTAMIDINE ON POLYAMINE LEVEL AND BIOSYNTHESIS IN WILD-TYPE, PENTAMIDINE-TREATED, AND PENTAMIDINE-RESISTANT LEISHMANIA

Polyamine biosynthesis was studied in wild-type promastigotes of Leish mania donovani and Leishmania amazonensis treated with pentamidine and in the parasites resistant to this drug. Treatment of wild-type clone s with low pentamidine concentrations for 24 hr provoked a strong decr ease in arginine, ornithine, and putrescine pools, while the level of intracellular spermidine remained unchanged, In these cells, the activ ity of the enzyme ornithine decarboxylase was found to be decreased. C ompared to wild-type cells, resistant clones had a lower level of putr escine, higher pools of arginine and ornithine, and a similar spermidi ne content. Analysis by Western blot and DFMO-binding showed reduced a mount of ornithine decarboxylase. Furthermore, in the resistant cells, the kinetic parameters of the enzyme spermidine synthase were markedl y changed, showing increased affinity to putrescine and decreased affi nity to pentamidine. Thus, it seems that polyamine biosynthesis pathwa y is a target of pentamidine in Leishmania and is altered in resistant clones. (C) 1997 Academic Press.