The malarial pigment in rat infected erythrocytes and its interaction with chloroquine. A Mossbauer effect study

Mossbauer studies of rat erythrocytes infected by Plasmodium berghei malaria parasites, using ⁵⁷Fe-enriched rat red blood cells, were carried out in order to determine the physical parameters which characterize the malarial pigment iron and to test the effect of the widely used antimalaria drug, chloroquine, on these parameters. The iron in the malarial pigment which is derived from hemoglobin digestion by the intracellular parasite was found to be trivalent, high spin, with Mossbauer parameters which are significantly different from those of any known iron porphyrin containing compound. No difference was found between the parameters obtained in erythrocytes infected by drug-sensitive and drug-resistant strains of P. berghei, both before and after the treatment with chloroquine. The iron compound consists of microaggregates, about 30 Å in diameter. These are somewhat larger in chloroquine-resistant strains and tend to increase in size in chloroquine-sensitive strains upon treatment with the drug. Mossbauer spectra of erythrocytes infected by a chloroquine-resistant strain revealed pigment iron in relative amounts invariable of those found in chloroquine-sensitive strains, demonstrating that drug-resistant parasites indeed digest hemoglobin.