Effect of high choline concentration on the inhibition of PC metabolism by F13. Infected erythrocytes (5 × 10⁶infected cells) were preincubated for 5 minutes in the presence of 10 μmol/L (•) or 200 μmol/L (○) choline. The drug was then added at the indicated concentration and after 5 minutes, and the PC biosynthesis assays were initiated by the addition of 10 μCi (³H)choline and pursued for 5 hours at 37°C.