Comparative ultrastructural study of the process of hemoglobin degradation by P. berghei (Vincke and Lips, 1948) as a function of the state of maturity of the host cell

By serial sectioning and 3D reconstruction we have been able to demonstrate that the type of system for hemoglobin digestion in two strains of Plasmodium berghei, N and RC, is dependent on the maturity of the host cell. In parasites growing in erythrocytes, both systems for the endocytosis of hemoglobin-micropinocytosis and the cytostomal system (i.e. a cytostome budding a cytostomal tube that releases food vacuoles)-are fully functional and produce a great quantity of residual pigment. Parasites growing in reticulocytes have a disrupted cytostomal system; no tube is formed and only food vacuoles are visible in their cytoplasm. Residual pigment is smaller in size and in quantity. The reduced quantity of pigment in reticulocytes is explained by our observation of the exocytosis of pigment. We propose a hypothesis that relates the process of degradation of hemoglobin to the maturity of the host cell and a possible mechanism of protection against chloroquine, a drug known for its affinity for malarial pigment.