Effects of 8-PCPT–cGMP on ZL-treated erythroid progenitors isolated from patients with homozygous sickle cell anemia. The experimental conditions were the same as in Figure 3. The effect of 8-(4-chlorophenylthio)guanosine 3′,5′-cyclic monophosphate (8-PCPT–cGMP; 10 μM) on BFU-E colony growth (A) and Hb F synthesis (B) in zileuton-treated (ZL; 50 μM) sickle erythroid progenitors was assessed. Data are expressed as the mean ± SEM. n = 7 in control (CON) and ZL treatment groups; n = 4 in the ZL + 8-PCPT–cGMP treatment group. Each experiment was done in triplicate. *P is less than .001 compared with the CON and ZL + 8-PCPT–cGMP treatment groups.