THE EFFECT OF PRAZIQUANTEL TREATMENT ON GLUTATHIONE CONCENTRATION IN SCHISTOSOMA-MANSONI

A fluorescent dye monochlorobimane (MCB) that binds glutathione (GSH) was used as a tool for measuring the concentration of GSH in skin and mechanically-transformed schistosomula. The specificity of MCB binding to GSH was confirmed by thin layer chromatography (TLC) and high perf ormance liquid chromatography (HPLC). The MCB binding to GSH is an ene rgy-dependent process since no labelling could be seen at low temperat ure. When 24-h-old schistosomula were depleted of GSH by buthionine su lfoximine (a specific inhibitor of GSH synthesis) for 18 h, a signific ant decrease (P < 0.001) in fluorescence was observed. PZQ treatment o f the schistosomula after first labelling the parasites with MCB did n ot greatly affect MCB binding to GSH. However, when the 24-h-old schis tosomula were first PZQ treated and afterwards labelled with MCB, the pattern of labelling was identical to that of those of the non-labelle d parasites. When 24-h-old schistosomula were first PZQ treated, washe d and labelled in the presence of 1 mM GSH, the level of fluorescence was recovered. These results suggest that PZQ depletes GSH from schist osomula, and may render them susceptible to the host's immune system.