Separation of erythrocytes infected with murine malaria parasites in metrizamide gradients

Density gradients with metrizamide, a tri-iodinated benzamido derivative of glucose, have been used to separate erythrocytes infected with 3 species of murine plasmodia. Good separations were obtained of uninfected erythrocytes from erythrocytes containing parasites in different developmental stages. With metrizamide solutions, the densities required for isopyenic separation can be obtained without hypertonicity or high viscosity, and the viability and those aspects of the metabolism of parasites and erythrocytes that we measured are not detectably modified by exposure to these solutions. This type of separation has many possible applications to biochemical and immunological investigations.