Arctic char (Salvelinus alpinus) metallothionein: cDNA sequence, expression, and tissue‐specific inhibition of cadmium‐mediated metallothionein induction by 17β‐estradiol, 4‐OH‐PCB 30, and PCB 104

Abstract

In this study, we haveexamined the basallevel expression and tissue‐specificexpressionpatternsof metallothionein (MT) in Arctic char following metal and E2 (17β‐estradiol) treatment. To study the gene regulation in Arctic char, the two MT isoforms were isolated from a lambda‐ZAP hepatic cDNA library and characterized. Determination of basal MT mRNA and MT expression for 10 different tissues revealed a lack of correlation between MT mRNA and MT levels. The inducibility of MT mRNA and the correlation to resulting MT levels were then determined for liver and kidney. We found a more rapid and stronger induction of MT mRNA in liver than in kidney at day 1 and 3 postinjection, whereas the MT protein quantification showed higher MT levels in kidney than in liver at days 3 and 7 postinjection. These discrepancies indicate that differences in metal handling or posttran‐scriptional regulation of MT exists between tissues. Whereas metals induce MT synthesis, E2 inhibit the hepatic MT expression. To examine the tissue specificity of this inhibition, we determined the effect of 17pj‐estradiol (E2) and two estrogenic PCBs (4′‐OH‐PCB 30 and PCB 104) on Cd‐mediated MT induction in liver and kidney. Although E2 and the estrogenic PCBs inhibited cadmium‐mediated hepatic MT induction, these compounds did not interfere with renal MT induction.

Multiwall Carbon Nanotube-Induced Apoptosis and Antioxidant Gene Expression in the Gills, Liver, and Intestine ofOryzias latipes

“…Previous studies demonstrated that estradiol or endocrine-disruptor chemicals could induce the expression of antioxidant genes, such as GST , but reduce CAT and MT expression [24, 28, 64]. At 14 days, the GST induction relative to the controls was higher in females than males, albeit not significantly so, while the induction of MT and CAT expression was significantly higher in males.…”

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“…In both species MT is upregulated towards the end of vitellogenesis [38,39] and is believed to sequester Zn from the liver in order to control the Zn homeostasis once vitellogenesis is over [45]. It has also been shown that E2 functions as an antagonist of MT induction in both rainbow trout [28] and Arctic char [46] further supporting the involvement of MT in reproduction. If Vtg requires Zn for proper tertiary folding, then upregulation of MT by cortisol could lead to a redistribution of Zn from Vtg to MT with degradation of Vtg as a consequence.…”

Population‐level consequences for wild fish exposed to sublethal concentrations of chemicals – a critical review

“…For example, oestrogens inhibit metallothionein induction in Arctic char ( Salvelinus alpinus , Salmonidae) exposed to cadmium (Gerpe et al . ). Of greater concern is when the effects of one chemical greatly increase the potency of another chemical.…”

“…There is also some evidence suggesting that exposure to one substance can affect exposure to others acting by different mechanisms. For example, oestrogens inhibit metallothionein induction in Arctic char (Salvelinus alpinus, Salmonidae) exposed to cadmium (Gerpe et al 2000). Of greater concern is when the effects of one chemical greatly increase the potency of another chemical.…”