JOYNER-MATOS, J.L.*; DOWNS, C.A.; JULIAN, D.; Univ. of Florida; EnVirtue Biotechnologies, Inc.; Univ. of Florida: Stress Protein Expression in the Surf Clam Donax variabilis Following Exposure to Normoxia, Hypoxia, Hyperoxia, and Hydrogen Sulfide.

The endogenous production of oxygen-centered free radicals and resulting oxidative damage may occur in tissues exposed to hypoxia, hyperoxia, or hydrogen sulfide. Previous investigations of oxidative damage from these stressors in marine invertebrates have produced conflicting results, perhaps because these studies utilized species that are presumably adapted to these stressors and therefore may not show strong evidence of oxidative damage or antioxidant response. To increase the likelihood of detecting oxidative stress, we examined the effects of these stressors in the surf clam Donax variabilis, which inhabits high-energy sandy beaches and is therefore unlikely to have specific physiological adaptations to these stressors. D. variabilis were exposed to hypoxia (~10 kPa Po₂), hyperoxia (~27 kPa Po₂), or hydrogen sulfide (~100 µM) for 24-hour experiments in a flow-through system. We used immunochemical analysis and dot blotting to quantify whole-animal expression levels of antioxidant (copper-zinc and manganese superoxide dismutases, glutathione peroxidase), stress (heme oxygenase, ferrochelatase, ubiquitin, glutathione), heat shock (60, 70, Grp75, small HSP), and oxidative damage repair proteins (HNE, MutY, and mitochondrial OGG-1). In general, antioxidant proteins and oxidative damage repair proteins increased two- to six-fold (p < 0.01) in all treatment groups in comparison to normoxic controls, with hyperoxic and sulfidic conditions inducing greater responses than hypoxia. Surprisingly, heme oxygenase, ferrochelatase, and sHSP, which have been reported to respond to hypoxia and hyperoxia in mammalian models, did not change significantly. This stress protein response in D. variabilis suggests that these abiotic stressors do induce oxidative damage, particularly in a species not adapted to these conditions.