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 essen tial metals and detoxify toxic metals, but that MT can also play a signific ant role as an antioxidant and can be induced by oxidative stresses other t han metals. This study is aimed at investigating the effect of hydrogen per oxide (H2O2), and the combined effect of H2O2 and cadmium (Cd) on MT induct ion and condition index (CI) in dogwhelks Nucella lapillus. Adult male dogw helks (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 + 0.5 0 PPm Cd; (4) 1.0 ppm H2O2 + 0.25 ppm Cd: (5) 2.0 ppm H2O2; (6) 1000 ppm H2 O2 or (7) 1000 ppm H2O2 + 0.50 ppm Cd. The concentration of MT in the Leibl ein 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 sugg esting that Cd antagonistically reduces toxicity caused by H2O2 since Cd-in duced MT may have a protective function against hydroxyl radicals. (C) 2001 Elsevier Science Ltd. All rights reserved.