Metallothionein induction and condition index of dogwhelks Nucella lapillus (L.) exposed to cadmium and hydrogen peroxide

It has been suggested that metallothionein (MT) not only can regulate essential metals and detoxify toxic metals, but that MT can also play a significant role as an antioxidant and can be induced by oxidative stresses other than metals. This study is aimed at investigating the effect of hydrogen peroxide (H₂O₂), and the combined effect of H₂O₂ and cadmium (Cd) on MT induction and condition index (CI) in dogwhelks Nucella lapillus. Adult male dogwhelks (27 ± 1 mm in shell length) were exposed for 20 days to (1) control (filtered natural seawater only); (2), 0.50 ppm Cd; (3) 2.0 ppm H₂O₂ + 0.50 ppm Cd; (4) 1.0 ppm H₂O₂ + 0.25 ppm Cd; (5) 2.0 ppm H₂O₂; (6) 1000 ppm H₂O₂ or (7) 1000 ppm H₂O₂ + 0.50 ppm Cd. The concentration of MT in the Leiblein gland of N. lapillus was quantified using the silver saturation method. MT or MT-like proteins in the animals were induced by Cd (0.5 ppm), H₂O₂ (2.0 ppm) or Cd + H₂O₂, indicating that MT in this gastropod species can be induced by either metal or oxidative stresses. Exposure to high H₂O₂ (1000 ppm) alone or combined with Cd, and exposure to Cd (0.50 ppm) or H₂O₂ (2.0 ppm), resulted in significant weight loss, indicated by a reduction of CI. However, CIs of groups (3) and (4) were similar to that of the control suggesting that Cd antagonistically reduces toxicity caused by H₂O₂ since Cd-induced MT may have a protective function against hydroxyl radicals. © 2001 Elsevier Science Ltd.