An Aspect of the Ribonucleic Acid Synthesis in Vitro in Free Parasites of Malaria (Plasmodium berghei)

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An aspect of ribonucleic acid (RNA) synthesis in malaria (Plasmodium berghei) was observed using free parasite cells in vitro. The time course of the incorporation of uridine-2-¹⁴C into parasite RNA showed a linearity up to one hour and then a plateau. The incorporation rate was directly proportional to the amount of malarial parasites used. The rate and the level of the uridine incorporation into parasite RNA were higher in K⁺-rich medium than in Na⁺-rich medium. Coenzyme A and dithiothreitol had no stimulative effect on the uridine incorporation into parasite RNA. Their addition had no protective effect also on the preservation of the RNA synthesizing capability of free parasites. The addition of adenosine, guanosine, and cytidine to the incubation mixture inhibited apparently the incorporation of uridine-2-¹⁴C into parasite RNA. When cytidine was omitted from those additions, no inhibition was observed. Dinitrophenol inhibited only 30% of the uridine incorporation and no further inhibition was observed by the further addition of the inhibitor. Actinomycin D inhibited 80% of the uridine incorporation at 0.5 μg/ml and that shows, in Plasmodium berghei, RNA synthesis is desoxyribonucleic acid (DNA) dependent.