Malarial Pigment-Dependent Error in the Estimation of Hemoglobin Content in Plasmodium falciparum-Infected Red Cells: Implications for Metabolic and Biochemical Studies of the Erythrocytic Phases of Malaria

Eugene F. Roth Jr.Division of Hematology, Montefiore Hospital and The Albert Einstein College of Medicine, 111 East 210th Street, Bronx, New York 10467

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Donna S. BrotmanDepartment of Medical and Molecular Parasitology, New York University School of Medicine, New York, New York 10016

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Jerome P. VanderbergDepartment of Medical and Molecular Parasitology, New York University School of Medicine, New York, New York 10016

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Seymour SchulmanDepartment of Medical and Molecular Parasitology, New York University School of Medicine, New York, New York 10016

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Measurements of mean corpuscular hemoglobin (MCH) in Plasmodium falciparum-infected red cells cultured in vitro revealed that malarial pigment (hemozoin) interferes with a true estimate of the actual hemoglobin content in Drabkin's reagent. When the hemozoin pigment was removed by passage of the lysate over a Biorex 70 column, a lower MCH value was obtained which allowed one to estimate that, under these conditions, the parasite consumes about 25% of the red cell's initial hemoglobin. Because spectrophotometric examinations of infected red cell lysates in Drabkin's reagent detect the unchanging heme content of infected red cells (hemoglobin + hemozoin), it can be used for expressing enzymatic activity or metabolite content. Results agree with simultaneous measurements on a per cell basis. However, it is suggested that instead of per gram hemoglobin, the activity should be stated as per mmole (or µmole) heme pigment. The ability to estimate accurately the consumption of intracellular hemoglobin will be useful in metabolic and pharmacologic studies of the parasite/red cell interaction.

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