THE IMPORTANCE OF HYDROGEN-PEROXIDE IN PHAGOCYTIC BACTERICIDAL ACTIVITY OF JAPANESE EEL NEUTROPHILS

The bactericidal activity of Japanese eel neutrophils in the presence of oxygen radical scavengers was investigated. Catalase inhibited bact erial killing, while superoxide dismutase and hydroxyl radical scaveng ers (D-mannitol, sodium benzoate) did not. Superoxide dismutase had no synergetic effect with catalase. These observations indicate that hyd rogen peroxide acts as a potent factor in the bactericidal process by eel neutrophils. The phagocytic index of cytochalasin B-treated neutro phils was less than one third of that of control neutrophils, although their phagocytic rate was more than 90%. Cytochalasin B, which inhibi ts phagosome formation without suppressing radical production, decreas ed the bactericidal activity of the neutrophils. and catalase did not affect the bacterial killing of cytochalasin B-treated neutrophils. Ex posure to hydrogen peroxide at concentrations, which are expected with in eel neutrophils during the respiratory burst, effectively killed th e bacteria tested. Thus, it is suggested that the hydrogen peroxide-de pendent bactericidal activity in eel neutrophils is expressed only wit hin phagosomes but not extracellularly and that phagosome formation is essential for this activity.