Metallothionein induction in cultured fibroblasts and liver of a marine flatfish, the turbot,Scophthalmus maximus

Abstract

Intraperitoneal injection of turbot with Cd induced the synthesis of a low molecular weight hepatic Cd-binding protein and a 500bp mRNA, which hybridised to a plaice metallothionein (MT) cRNA probe. The Cd-binding protein displayed cross-reactivity in a competitive ELISA with antiserum raised against rainbow trout MT and had the characteristic amino acid composition, metal stoichiometry and spectral characteristics of a Class I MT. Only one isoform was apparent on ion exchange chromatography. Southern blot analysis of DNA cleaved with four restriction enzymes suggested that only a single MT gene is present in turbot.In an established turbot fibroblast cell line, Cd induced MT mRNA and MT levels in a dose and time-dependent manner. MT was also induced by Cu, Hg and Zn but not Pb exposure. Physiological concentrations of glucocorticoids and sex hormones did not induce MT synthesis, although at high concentrations a positive response to corticosterone, dexamethasone, hydrocortisone or progesterone was observedin vitro indicating the possible presence of a functional steroid regulatory element in the fish MT gene.

The use of bioaccumulation, biomarkers and histopathology diseases in shape Procambarus clarkii to establish bioavailability of Cd and Zn after a mining spill

“…Consequently, it was shown a decrease in metallothionein concentration in males when they were exposed to 3000 μg L −1 of zinc. The decrease of MT concentrations with increasing zinc exposure observed at the present study with male P. clarkii was also described in some laboratory exposures of invertebrates to dissolved availabilities of trace metals, probably as a result of toxic effect preventing detoxification processes from being fully functional (George et al, 1992;Barka et al, 2001). This hypothesis has been enlarged to other detoxification mechanisms based upon the induction of specific proteins such as cytochrome P450-dependant monooxygenases (Flammarien, 2000).…”

Oxidative damage effects in the copepod Tigriopus japonicus Mori experimentally exposed to nickel

“…The inhibitory effect of Ni additions on MT synthesis in the initial exposure time might be attributable to the ''spill-over'' hypothesis which deems that when the cellular store of MT is insufficient to capture heavy metals, the excess will ''spill-over'' and combine with other cellular ligands, hence engendering metal toxicity (Brown and Parsons 1978). Several laboratory studies with experimental organisms exposed to a series of metal concentrations demonstrate that high metal treatment could suppress MT level, the possible result of which being that metal attack might destroy the detoxification function of MT (George et al 1992;Mouneyrac et al 2002). For example, Mouneyrac et al (2002) found that Cu and Zn exposures show little or even restraining impact on MT production in Orchestia gammarellus.…”

Effects of environmental factors on low-molecular-weight peptides of fishes: a review

“…The thiol groups of cysteine residues form complexes with Cd 2+ at a molar ratio of 3 : 1, which leads to the appearance of a characteristic peak of absorption at 250 nm. Different flatfish species (e.g., turbot Scotophthalmus maximus ), cod ( Gadus morhua ), pike ( Esox lucius ), and bearded stone loach ( Nemachilus barbatulus ) contain one form of hepatic MT (Shears and Fletcher, 1985;George et al , 1992); rainbow trout ( Oncorhynchus mykiss ), red sea bream ( Pagrus major ), channel catfish ( Ictalurus punctatus ), and goldfish ( Carassius auratus ) contain two forms of this protein (Kuroshima, 1995;Zhang and Schlenk, 1995). Two MT isoforms corresponding to classes MT-I and MT-II (6227 and 6435 Da, 34.2 and 31.9% of cysteine residues, respectively) were isolated from the hepatopancreas of the carp ( Cyprinus carpio ) (Kito et al , 1982a).…”