Osmotic Fragility of Normal Duck Erythrocytes as Influenced by Extracts of Plasmodium lophurae, P. lophurae-Infected Cells, and Plasma

Abstract

Osmotic fragility of normal duck erythrocytes was significantly increased after exposure in vitro to cell-free extracts of Plasmodium lophurae or P. lophurae-infected duck red cells. The extent of the effect could be correlated with the developmental stage of the parasite, the effect being greater when most of the parasites were late segmenting forms than when they were mostly young trophozoites. The effect is apparently derived from the parasites themselves rather than from the infected erythrocytes. However, extracts from normal duckling erythrocytes also possess an osmotic fragilityinducing capacity which proved to be greater than that of erythrocytes parasitized by young trophozoites. This demonstrated further the effect of the extract of late segmenting forms of the parasite in inducing osmotic fragility. Plasma from infected ducklings could also produce an increased osmotic fragility of normal duck red cells in vitro. Whether the osmotic fragility of erythrocytes in malarial infections is altered has been the subject of many studies: Geiman et al. (1946), Shen et al. (1946), Laser (1948), and Devakul and Maegraith (1959) with primate malaria; Danon and Gunders (1962) with rodent malaria; and Fogel et al. (1966) with both, plus human and avian malarias, all of which indicate that osmotic fragility is increased. However, that osmotic fragility of red cells in malaria remains unaltered has been suggested by several early studies (Foy and Kondi, 1943; Foy, 1948). The present report is the result of an investigation of the effects of extracts of Plasmodium lophurae with and without red cells at various stages of the parasite's life cycle upon the osmotic fragility of washed, normal duckling red cells in vitro. The effects of plasma upon the osmotic fragility of such erythrocytes have similarly been studied as well as the effect of the soluble material within infected erythrocytes exclusive of the parasites. MATERIALS AND METHODS