Formation of uric acid precipitates in <i>P. falciparum</i>-infected erythrocytes is dependent on exogenous hypoxanthine.

<p><i>P. falciparum</i>-infected erythrocytes were cultured in hypoxanthine free (A) and hypoxanthine-supplemented media as the unique purine source (B, 5 µM; C, 250 µM, D, 500 µM). Uric acid antibodies label precipitates within infected parasites <i>in vitro</i>. DAPI labels nuclei (blue). Bar is 5 µm. (E) Quantitation of infected erythrocytes that are positive for uric acid immunostaining. Data are displayed as mean ± SEM (n>100 schizonts in duplicate, from three independent cultures). (F) Quantitation of uric acid in lysate fractions of purified <i>P. falciparum</i> schizonts cultured in increasing hypoxanthine concentrations: Hx- [0 µM Hx] (light grey), 250 µM Hx (dark grey) and 500 µM Hx (black). Ultracentrifugation was performed on lysates to obtain supernatant (SN) and pellet fractions. Uninfected erythrocytes (RBC; white) were processed in parallel. Quantitation of uric acid using a colorimetric absorbance assay is shown. Data are displayed as mean ± SEM (n = 3 independent cultures; *p<0.05 relative to Hx- [0 µM Hx] pellet control).