The influence of magnesium ion and ascorbic acid on the erythrocytic schizogony of Plasmodium vivax.

Asexual erythrocytic stages of Plasmodium vivax have been cultivated for one schizogonic cycle to investigate parasite requirements for metal ions and vitamins. Waymouth and RPMI 1640 (GIBCO) media were used in varying proportions resulting in varying concentrations of organic salts, vitamins, and growth factors. A 1:3 mixture gave the highest percentage (62.6%) of parasite development from the amoeboid forms to mature segmenters after 44 h of cultivation in a candle jar atmosphere at 38.5 degrees C. Nevertheless, the total parasite count was significantly higher (P less than 0.50) in the mixture which had a Waymouth: RPMI ratio of 1:2. Differentiation of schizonts to merozoites as well as parasite counts could be further enhanced by the addition of magnesium chloride to a final concentration of 1.8 mM magnesium ions. The minimal requirement for ascorbic acid which was studied in Science Mahidol (SCMI 612) medium appeared to vary among isolates. For example, all parasite population of four isolates tested declined proportionally with the decrease in concentration of ascorbic acid, the critical point being 3 micrograms/ml medium. However, two isolates used in this study could no longer differentiate to segmenters when the ascorbic acid concentration of the medium was less than 6 micrograms/ml.