[Effects of four drugs on intraerythrocytic Plasmodium yoelii of early and late stages].

Erythrocytes of mice infected with Plasmodium yoelii of early stage (ESP) were separated from those infected with late stage (LSP), by a single density-gradient centrifugation in 19% diatrizoate meglumine. After centrifugation, the differential counts of ESP and LSP were 84.9% and 87.4%, respectively. The stage-dependent effects of nitroquine (NQ), pyrimethamine (Pyr), perphenazine (Per) and metronidazole (Met) were studied with [3H]adenosine incorporation into ESP and LSP in vitro using chloroquine (CQ) as control. Like CQ, the 4 drugs inhibited that [3H]adenosine incorporation into LSP more remarkably than that into ESP. The IC50 of CQ, Met, Pyr, Per, and NQ against ESP were 1.89, 2.11, 2.56, 2.60, and 4.65 times as high as that against LSP, respectively.