HEMOLYSIS OF PLASMODIUM-FALCIPARUM TROPHOZOITE-INFECTED ERYTHROCYTES AFTER ARTEMISININ EXPOSURE

This study has examined in vitro, how exposure to the antimalarial dru g artemisinin affects Plasmodium falciparum and its host erythrocytes. Factors examined include: cell morphology, intracellular haemoglobin levels, and haemoglobin catabolism (haemozoin production). To avoid un infected erythrocytes complicating the study, P. falciparum ring-infec ted erythrocytes were concentrated to 99% parasitaemia, by saponin hae molysis, before the parasites were grown with or without artemisinin. Without artemisinin, the parasites completed their life cycle in the n ormal time (40 h), during which a mean of 980 pmol of ferriprotoporphy rin IX from haemoglobin was incorporated into haemozoin per 10(6) para sitized erythrocytes, and intracellular haemoglobin level decreased by 90%. Exposure of ring-infected erythrocytes to artemisinin (250 ng pe r ml of culture medium) inhibited parasite growth completely, haemozoi n production by 95%, and decreased the intraerythrocytic haemoglobin l evel by 90%; the infected erythrocytes remained intact during the 64 h of study. Haemozoin production was also inhibited when the drug was a dministered at the trophozoite stage of parasite growth, but the infec ted erythrocytes haemolysed. These findings may contribute to understa nding of antimalarial actions of artemisinin that promote parasite cle arance.