The accumulation, metabolism, and distribution of acriflavin (acr) in two culture strains of Leishmania tarentolae were studied. One strain, reported previously, was sensitive to the dye, i.e. became dyskinetoplastic and could not be subcultured in the presence of 470 ng/ml acr, and one was resistant. Accumulation was studied by fluorescence of the dye within cells and by uptake of acr-3H by cells. Metabolism was studied by paper chromatography of aqueous extracts from cells grown with acr-3H, and distribution was examined by fluorescence and quantitative electron microscope radioautography. Substances affecting the response to acr included hemin and an acr-sensitizing factor initially obtained from red cells but here shown to be distinct from hemoglobin. In the presence of the sensitizing factor or in the absence of hemin, the resistant strain became dyskinetoplastic and could not be subcultured. Acr fluorescence appeared in the nucleus of the resistant strain, and the percentage of radioautography grains appearing in the nucleus increased. Under these conditions the distribution of radioactivity from chromatographed extracts was altered from the normal in a similar fashion. Because sensitization of the resistant strain is associated with increased amounts of acr in the nucleus, that organelle may be implicated in the mode of action of acr. In general, the two strains behaved alike except for (a) the response to acr, (b) the arginine requirement for optimal growth, and (c) the sensitivity to cycloheximide. Thus, one cannot exclude the wider possibility that acr may act on the cytoplasm and the nucleus as well as on the mitochondrion.

This content is only available as a PDF.