Total oxyradical scavenging capacity (TOSC) in polluted and translocated mussels: a predictive biomarker of oxidative stress

Several classes of environmental pollutants are known to enhance the intrac ellular formation of reactive oxygen species in marine invertebrates with d ifferent consequences on their antioxidant system. Despite variations in th e endogenous levels of antioxidants may reveal biological effects induced b y pollutants, the overall efficiency of antioxidant system is not evaluated from such data. The total oxyradical scavenging capacity (TOSC) assay meas ures the biological resistance to various kinds of oxyradicals, thus provid ing useful indications to predict oxyradical-mediated adverse effects on th e physiological condition of the organisms. In the present work, the capabi lity to neutralize three patent cellular oxidants (peroxyl radicals, hydrox yl radicals and peroxynitrite) was compared in two natural populations of m ussels from a clean and a metal polluted area, respectively. and in control organisms translocated for 8 weeks to the contaminated site. Within each g roup of mussels, the relative efficiency towards the various forms of oxyra dicals, showed peroxyl radicals and hydroxyl radicals as the less and the m ost difficult species, respectively, to neutralize by cellular antioxidants . When the two populations were compared, polluted organisms revealed a sig nificantly higher susceptibility to oxidative stress as indicated by their lower TOSC values. A significant reduction of antioxidant capacity was obse rved also in translocated organisms where only a moderate recovery was evid ent at the longer exposure time. Separation of soluble antioxidants from th e protein fraction, suggested a greater depletion of low molecular weight m olecules during the first phase of exposure to pollutants. The pollutant-in duced impairment of antioxidant capability precludes the appearance of oxyr adical toxicity. In the present study a high correlation was obtained betwe en reduced TOSC values and lower Neutral Red retention time in lysosomal co mpartment of circulating haemocytes. The TOSC towards different forms of ox yradicals is confirmed an useful biomarker with predictive validity at the organism level. (C) 2000 Elsevier Science B.V. All rights reserved.