Distinctive accumulation patterns of Cd(II), Cu(II), and Cr(VI) in tissue of the South American teleost, pejerrey (Odontesthes bonariensis)

The time- and concentration-dependent accumulation patterns of three environmentally relevant metals, with different chemical and biological properties, were comparatively evaluated in tissue of South American fish, pejerrey (Odontesthes bonariensis). Six-month-old juvenile pejerrey were exposed to 1, 5, or 10 μg l−1 of Cd2+; 10, 50, or 100 μg l−1 of Cu2+; or 100, 500, or 1000 μg l−1 of Cr6+ during 16 days. Tested concentrations ranged from those that caused no significant accumulation to those that induced growth reduction or even mortality (Cd and Cu). Concentration-dependent accumulation of Cd and Cr presented similar patterns, characterized by a linear and exponential relationship in the gill and liver, respectively, with a greater slope at longer exposure times. Differently, essential Cu showed a linear relationship in both tissues, and no slope increase was observed in the gill. The gill time-dependent accumulation pattern of Cd exhibited relatively long times to half-saturation (t1/2(1) = 36.6 days) and high-saturation values (S(1) = 205.4 nmol g−1). The opposite pattern was observed for Cu (t1/2(100) = 0.6 days; S(100) = 24.4 nmol g−1), while Cr showed an intermediate position (t1/2(1000) = 2.8 days; S(1000) = 50.2 nmol g−1). In the liver, times to half saturation for the three metals were as follows: Cd = 4.7 days; Cu = 2.5 days; Cr = 1.6 days. Conversely, different saturation concentrations were observed among metals, Cu (S(100) = 102) presenting the highest values, Cd (S(10) = 4.4) the lowest, and Cr presenting an intermediate position (S(1000) = 24.7). Bioconcentration of non-essential Cd was high in the gill (2000-fold) and low in the liver (50-fold). On the other hand, the essential element Cu was poorly retained by the gill (15-fold) and accumulated mainly in the liver (50-fold). Differently, Cr was quickly and evenly accumulated by both organs, but barely bioconcentrating (2.5- and 1.5-fold levels as compared to the original in the gill and liver, respectively). The ratio of gill/liver concentration in exposed fish clearly differed from that of non-exposed fish, and was characteristic for each metal (Cd > 1; Cu < 1; Cr < 9), representing a potential tool to assess exposure. The accumulation patterns of studied metals in the tissue of pejerrey corresponded more with those reported for sensitive than for tolerant fish species. Distinctive tissue accumulation patterns in relation to growth reduction and non-acute lethality suggests different target tissues for sub-chronic effects, and would partially explain differences in the relative toxicity of these metals.