title: Heme polymerase activity and the stage specificity of antimalarial action of chloroquine.
abstract: Plasmodium falciparum lysate, prepared from 2.7 x 10(7) ring-infected erythrocytes and incubated with hemoglobin in sodium acetate at pH 5, incorporated a mean of 1.6 nmol of ferriprotoporphyrin IX (FP) into hemozoin in 18 to 22 hr. A similar preparation of trophozoite lysate incorporated a mean of 3.6 nmol of FP into hemozoin in 4 to 6 hr. These findings indicate differences between heme polymerase activity (hemozoin production) at the ring and trophozoite stages of malaria parasites. Intracellular hemozoin production was 90% inhibited at the ring and trophozoite stages by 0.5 and 7 nmol of chloroquine/10(6) infected erythrocytes. respectively. The inhibition killed the rings but not the trophozoites, suggesting that mature parasites may have a mechanism for protecting themselves against chloroquine-FP toxicity.
authors.affiliation: MLS Department, Faculty of Allied Health Sciences, Kuwait University, Arabian Gulf.
authors.forename: A U
authors.initials: AU
authors.lastname: Orjih
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D002738:Chloroquine / Q000493:pharmacokinetics / Q000494:pharmacology*; D006420:Hemeproteins / Q000096:biosynthesis; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000201:enzymology; D014166:Transferases / Q000037:antagonists & inhibitors*
chemical_list: D000962:Antimalarials; D006420:Hemeproteins; C020753:hemozoin; D002738:Chloroquine; D014166:Transferases; C072176:heme polymerase