Characterization of the chemiluminescence measured in hemocytes of the Eastern oyster, Crassostrea virginica

Hemocytes of the Eastern oysters, Crassostrea virginica, produce reactive oxygen intermediates (ROIs) during phagocytosis to destroy foreign cells. Although evidence suggests that oyster hemocytes generate superoxide anions (Oz) following phagocytic stimulation, the production of other ROI species such as hydrogen peroxide (H2O2), singlet oxygen (O-1(2)), hydroxyl radical (. OH), and hypochlorous acid (HOCl) has not been directly investigated. In this study, ROI production by oyster hemocytes was measured by quantifying the production of chemiluminescence (CL) amplified with different luminescent probes. The ROIs involved in CL production were identified by testing the effects of scavengers and inhibitors of particular ROI species on CL. Taurine completely inhibited luminol-dependent CL, indicating that HOCl production was primarily responsible for the CL generated by hemocytes during phagocytosis of yeast granules. In addition, azide strongly inhibited luminol CL, implicating the involvement of myeloperoxidase in the production of HOCl and the resulting CL. Superoxide dismutase partially inhibited CL, indicating that superoxide ions were also produced and contributed to CL. Luminol CL was significantly higher in hemocytes from oysters heavily infected with the parasite Perkinsus marinrcs and remained completely inhibitable by taurine suggesting that HOCl production was enhanced by infection. Last, the concentration of taurine measured in oyster hemolymph was sufficient to quench a significant amount of the HOCl generated by the hemocytes and may reduce the effectiveness of the oyster's defense response to infections. (C) 1995 Wiley-Liss, Inc.