Nitric oxide mediates metabolic functions in the bivalve Arctica islandica under hypoxia

Short description of experiments and analyses: The formation of nitric oxide (NO) was examined in live hemocyte cells and gill filaments of the bivalve Arctica islandica at different partial pressures of oxygen (pO₂; measurements conducted with ISO-NOP electrode & confocal microscopy). To establish whether cellular NO formation of A. islandica is catalyzed enzymatically, NO production was measured in the presence and absence of the nitric oxide synthase inhibitor (L-NAME). In a second set of experiments, the effect of chemically (by spremineNONOate) produced NO on gill respiration and cytochrome-c-oxidase activity was examined during phased reduction of pO₂ (16 kPa-2 kPa; measurements conducted with oxygen meter & spectrophotometer). Further, nitrite and nitrate contents were determined in the hemolymph of bivalves after 3.5 days of exposure to normoxic, hypoxic, and anoxic conditions (measurements conducted with microplate reader).