Malaria in studies in vitro. III: the protein synthesising activity of Plasmodium falciparum in vitro after drug treatment in vivo.

Aotus trivirgatus monkeys with established infections of Plasmodium falciparum were treated orally with either chloroquine or the novel compound 1-amidino-3-(3-chloro-4-cyanophenyl) urea. Blood samples were cultured in vitro, 18 hours after treatment, when no morphological abnormalities were apparent. The incorporation of radioactive leucine from the medium by the blood of treated monkeys was compared with that of the undosed control. Parasite maturation was also examined. Both chloroquine and the amidinourea were effective against the drug sensitive strain of P. falciparum. The combined use of an in vivo and in vitro test demonstrated that biochemical disturbance of the parasite may be demonstrable before morphological effects are seen. This system should prove useful in drug metabolism studies and in experiments using large or expensive animals.