Metallothionein induction and condition index of dogwhelks Nucella lapillus L.) exposed to cadmium and hydrogen peroxide Kenneth M.Y. Leung * , Robert W. Furness Institute of Biomedical and Life Sciences, Graham Kerr Building, University of Glasgow, Glasgow G12 8QQ, UK Received 26 April 2000; accepted 12 June 2000 Abstract It has been suggested that metallothionein MT) not only can regulate essential metals and detoxify toxic metals, but that MT can also play a signi®cant role as an antioxidant and can be induced by oxidative stresses other than metals. This study is aimed at investigating the eect of hydrogen peroxide H 2 O 2 ), and the combined eect of H 2 O 2 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 ®ltered natural seawater only); 2), 0.50 ppm Cd; 3) 2.0 ppm H 2 O 2 + 0.50 ppm Cd; 4) 1.0 ppm H 2 O 2 + 0.25 ppm Cd; 5) 2.0 ppm H 2 O 2 ; 6) 1000 ppm H 2 O 2 or 7) 1000 ppm H 2 O 2 + 0.50 ppm Cd. The concentration of MT in the Leiblein gland of N. lapillus was quanti®ed using the silver saturation method. MT or MT-like proteins in the animals were induced by Cd 0.5 ppm), H 2 O 2 2.0 ppm) or Cd+H 2 O 2 , indicating that MT in this gastropod species can be induced by either metal or oxidative stresses. Exposure to high H 2 O 2 1000 ppm) alone or combined with Cd, and exposure to Cd 0.50 ppm) or H 2 O 2 2.0 ppm), resulted in signi®cant 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 H 2 O 2 since Cd-induced MT may have a pro- tective function against hydroxyl radicals. Ó 2001 Elsevier Science Ltd. All rights reserved. Keywords: Antioxidant; Biomarker; Oxidative stress; Metallothionein; Metal binding protein 1. Introduction Metallothioneins MT) are low molecular weight ca. 6±10 kDa), cysteine-rich 25±33%) proteins which are induced by, and bind with Cu, Zn, Cd, Hg, Ag and Au e.g. seven equivalents of Zn and/or Cd or Cu per mole MT) Carpen e, 1993; Aspholm and Hylland, 1998). The major functions of MT in invertebrates include regula- tion of essential metals e.g. Zn and Cu) and detoxi®- cation of toxic metals e.g. Cd and Hg) Rosijadi, 1992, 1996). Therefore, it has been proposed that MT can be used as biomarkers for metal pollution Bebianno and Machado, 1997). Research on mammals has demonstrated that MT also play a signi®cant role as antioxidants like gluta- thione) and can be induced by other oxidative stresses. For example, rabbit liver Cd, Zn)±, Zn±, and Cd±MT can defend against hydroxyl and superoxide radicals Thornalley and Vasak, 1985). Metallothionein induc- tion by pre-treatment of mice with zinc protected against nickel-induced mortality and hepatic lipid peroxidation Srivastava et al., 1993). Although MT induction by metals, especially Cd, has been widely studied in marine molluscs, very few in vivo study in molluscs has been Chemosphere 44 2001) 321±325 www.elsevier.com/locate/chemosphere * Corresponding author. Present address: School of Biolog- ical Sciences, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK. E-mail address: k.leung@rhbnc.ac.uk K.M.Y. Leung). 0045-6535/01/$ - see front matter Ó 2001 Elsevier Science Ltd. All rights reserved. PII:S0045-653500)00297-6