Effect of pH on the cytoadherence of PEs to hCD36, mCD36, rCD36, H242Y, and Y242H. Adhesion assays were performed using transiently transfected COS-7 cells expressing human CD36, murine CD36, rat CD36, H242Y (human CD36 with residue 242 altered to tyrosine), or Y242H (rat CD36 with residue 242 altered to histidine). Infected blood suspended in BTS (pH adjusted by HCl or NaOH) to a 5% hematocrit and 5% parasitemia was added and incubated under continuous agitation for 90 minutes. After washing, adherence was quantitated microscopically by counting the number of adherent erythrocytes per transfected COS cell for at least 40 representative COS-7 cells per data point. Values indicated are for (A) human CD36 (•), rat CD36 (▪), and H242Y (□) and for (B) human CD36 (•), rat CD36 (▪),mouse CD36 (○), and Y242H (□). The values are mean values with standard deviations represented by error bars. Similar results were obtained in three independent experiments. Cytoadherence to human CD36 and Y242H is significantly pH dependent (P < .005, by ANOVA).