Biochemical responses in aquatic animals: A review of determinants of oxidative stress

The study of biochemical responses in aquatic animals comprises a vigorous area of inquiry within ecotoxicology for a number of reasons, including the perceived need for basic research in the field, the desire for highly sensitive biomarkers useful for biomonitoring and the particular concern for elevated rates of neoplasia observed in some aquatic systems. In this paper, an approach only recently investigated by aquatic toxicologists will be described and reviewed in detail. This approach is based on theories of oxyradical generation and subsequent oxidative stress in biological systems. Of particular concern to environmental toxicologists with respect to these phenomena are the abilities of a number of common and diverse compounds to undergo enzymatically facilitated redox cycling in cells and thereby generate oxyradicals under aerobic conditions. Mechanisms of oxyradical generation, toxicological consequences of these processes and endogenous antioxidant defense systems are described. In addition, methodologies for studying these phenomena are discussed and recent studies demonstrating their applicability to aquatic toxicology are reviewed.