Hemocyte-derived reactive oxygen intermediate production in four bivalve mollusks

Luminol-dependent chemiluminescence (LDCL) and nitroblue tetrazolium (NBT) reduction assays have been used to measure reactive oxygen intermediate (ROI) production by oyster (Crassostrea virginica) hemocytes, as well as ROI modulation caused by disease or exposure to environmental toxicants. However, ROI responses measured by these tests apparently vary considerably among other bivalve species. In all species tested, unstimulated hemocytes produced small quantities of ROIs. In C. virginica and Geukensia demissa phagocytosis or treatment with phorbol myristate acetate triggered significantly augmented, but kinetically dissimilar, ROI responses; however, no induction was recorded in two clam species (Mya arenaria and Mercenaria mercenaria). This was supported by both LDCL and NBT assays, measuring activity of the myeloperoxidase/hydrogen peroxide system and production of intracellular superoxide anion, respectively. The failure of the clams to respond to standard ROI-eliciting procedures is possibly indicative of interspecies differences in hemocyte-mediated antimicrobial defense mechanisms.