Influence of medium osmolality on the in vitro growth of Plasmodium falciparum: a morphologic and radioisotopic study.

The study of the growth rate and incorporation of [3H]hypoxanthine and [14C]isoleucine showed that in vitro variations of Plasmodium falciparum parasitemia levels and incorporation rates of the two radiolabeled molecules have been correlated. In our experimental conditions, P. falciparum blood forms in vitro tolerate osmolalities ranging from 180 to 360 mOSM. A weak hypo-osmolality (241 mOSM) favored the development of the parasite. The highest sensitivity of the parasite to osmotic variations was observed during schizogony. The merozoite stage and reinvasion process seemed less affected by hypo-osmolalities than by hyperosmolalities. The minor alterations in morphology of the parasites in hypo- and hyperosmotic media suggested that P. falciparum may have efficient osmoregulatory power.