Fig. 3.

Inhibition of in vitro-cultured P. falciparum (3D7). (A) Stage-dependent susceptibility. T4 was added at various concentrations to synchronized parasites in culture at ring (4 h) (•), trophozoite (22 h) (▪), or schizont (33 h) (▴) stages. Incubation was continued for 4 h, cells were washed twice and resuspended in fresh complete medium. (B) Time course of P. falciparum growth inhibition. T4 was added at 40 nM to synchronized cultures at ring, trophozoite, and schizont stages (see symbols above). After incubation for the indicated times, cells were washed twice and resuspended in fresh complete medium. For both of the experiments, [³H]hypoxanthine (0.7 μCi per well; 1 Ci = 37 GBq) was added at 52 h to monitor parasite viability. Reactions were stopped at 76 h, and parasitemia were evaluated for each stage and expressed as a percentage of the control (without drug). The results are expressed as means ± SEM (n ≥ 3).