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 intracellular formation of reactive oxygen species in marine invertebrates with different consequences on their antioxidant system. Despite variations in the endogenous levels of antioxidants may reveal biological effects induced by pollutants, the overall efficiency of antioxidant system is not evaluated from such data. The total oxyradical scavenging capacity (TOSC) assay measures the biological resistance to various kinds of oxyradicals, thus providing useful indications to predict oxyradical-mediated adverse effects on the physiological condition of the organisms. In the present work, the capability to neutralize three potent cellular oxidants (peroxyl radicals, hydroxyl radicals and peroxynitrite) was compared in two natural populations of mussels from a clean and a metal polluted area, respectively, and in control organisms translocated for 8 weeks to the contaminated site. Within each group of mussels, the relative efficiency towards the various forms of oxyradicals, showed peroxyl radicals and hydroxyl radicals as the less and the most difficult species, respectively, to neutralize by cellular antioxidants. When the two populations were compared, polluted organisms revealed a significantly higher susceptibility to oxidative stress as indicated by their lower TOSC values. A significant reduction of antioxidant capacity was observed also in translocated organisms where only a moderate recovery was evident at the longer exposure time. Separation of soluble antioxidants from the protein fraction, suggested a greater depletion of low molecular weight molecules during the first phase of exposure to pollutants. The pollutant-induced impairment of antioxidant capability precludes the appearance of oxyradical toxicity. In the present study a high correlation was obtained between reduced TOSC values and lower Neutral Red retention time in lysosomal compartment of circulating haemocytes. The TOSC towards different forms of oxyradicals is confirmed an useful biomarker with predictive validity at the organism level.
Regoli
F
Istituto di Biologia e Genetica, Università di Ancona, Via Ranieri, Monte D'Ago, I-60100, Ancona, Italy