Glutathione, glutathione S-transferase, and glutathione conjugates, complementary markers of oxidative stress in aquatic biota

Contaminants are ubiquitous in the environment and their impacts are of increasing concern due to human population expansion and the generation of deleterious effects in aquatic species. Oxidative stress can result from the presence of persistent organic pollutants, metals, pesticides, toxins, pharmaceuticals, and nanomaterials, as well as changes in temperature or oxygen in water, the examined species, with differences in age, sex, or reproductive cycle of an individual. The antioxidant role of glutathione (GSH), accompanied by the formation of its disulfide dimer, GSSG, and metabolites in response to chemical stress, are highlighted in this review along with, to some extent, that of glutathione S-transferase (GST). The available literature concerning the use and analysis of these markers will be discussed, focusing on studies of aquatic organisms. The inclusion of GST within the suite of biomarkers used to assess the effects of xenobiotics is recommended to complement that of lipid peroxidation and mixed function oxygenation. Combining the analysis of GSH, GSSG, and conjugates would be beneficial in pinpointing the role of contaminants within the plethora of causes that could lead to the toxic effects of reactive oxygen species.