Generation of oxygen radicals in hemocytes of the snail Lymnaea stagnalis in relation to the rate of phagocytosis

Abstract The kinetics of oxygen radical production by phagocytosing hemocytes of the pond snail Lymnaea stagnalis were investigated. After contact had been established between zymosan and hemocytes in monolayers at 0°C, phagocytosis was initiated by a shift to room temperature. Until the internalization phase of phagocytosis was completed, oxidative activity was detected mainly extracellularly (superoxide dismutase inhibitable cytochrome C reduction and peroxidase-catalyzed phenol red oxidation were used for the detection of superoxide and hydrogen peroxide, respectively). Thereafter, extracellular oxygen radical production by phagocytosing hemocytes decreased. Luminol-dependent chemiluminescence activity grew and, after the internalization phase of phagocytosis, remained at a high level, suggesting continued oxygen radical activity intracellularly. These results indicate that contact between zymosan and the hemocyte's plasma membrane stimulates a membrane-bound system to generate and release oxygen radicals. After internalization, this system appears to continue oxygen radical production inside the phagosome. So far, oxygen radical production in snail hemocytes shows many similarities to the mechanism in mammalian leucocytes.