Metallothionein induction by Cu, Cd and Hg in Dicentrarchus labrax liver: Assessment by RP-HPLC with fluorescence detection and spectrophotometry

Metallothionein was quantified in sea bass Dicentrarchus labrax intraperitoneally (i.p.) injected with different Cu, Cd and Hg doses (50–250 μg kg–1 wet wt) after 48 h exposure. A distinct peak with 16.8 min retention time was obtained by reversed-phase high performance liquid chromatography coupled to fluorescence detection (RP-HPLC-FD) with the three metals. Total metallothionein levels assayed in unheated liver extracts by RP-HPLC-FD were significantly higher (1.3–1.95-fold) than those obtained by the well-established spectrophotometric method. In the RP-HPLC-FD method, metallothionein increased linearly with Cu and Hg doses, being saturated beyond 100 μg kg–1 Cd. Maximum induction was obtained at 100 μg kg−1 Cd (5.3-fold), and 250 μg kg−1 Cu or Hg (8- and 5.1-fold, respectively). At low doses no metallothionein induction was shown by the less sensitive spectrophotometric assay.