Fig. 4. Production of superoxide (revealed by changes in DH2 fluorescence) and peroxide (CFH2 fluorescence) in the cell types studied. One experiment representative of four is shown. 0 = control, untreated cells; 1 or 2 = 1 or 2 h of incubation with 5 µM STS (HL-60 and HCW-2 cells) or with CHX and TNF- (U937 and BHT-pretreated U937 cells), respectively.