Preferential action of chloroquine on Plasmodium within mature erythrocytes

: In vitro studies on the effects of chloroquine on Plasmodium berghei in relation to the age of the host cell made it possible to demonstrate the preferential effect of the drug on parasites growing in mature red blood cells. The ED-50 for parasites in mature red blood cells is lower (1,64 +/- 0,2 mg/kg/day) than in reticulocytes (2,45 +/- 0,2 mg/kg/day). The result of clumping test for chloroquino-sensitive P. berghei growing in young red blood cells, is almost similar as in a chloroquino-resistant strain of the same species. These results are compared with physiological observations on Plasmodium host parasite relationships and bioclinical discrepancies noticed between in vivo chloroquine sensitivity of P. falciparum wild strains versus in vitro testing.