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

Abstract-In this study, we have examined the basal level expression and tissue-specific expression patterns of metallothionein (MT) in Arctic char following metal and E2 (17␤-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 posttranscriptional 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 17␤-estradiol (E2) and two estrogenic PCBs (4Ј-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.

Effects of steroid hormones on reproduction- and detoxification-related gene expression in adult male mosquitofish, Gambusia affinis

“…In the present study, all hormone treatments did not result in the significant change of MT mRNA expression in the liver of male mosquitofish as compared with the control. The lack of induction of MT mRNA by the steroid hormones is in accordance with some previous studies on rainbow trout (Olsson et al, 1995) and Arctic Char (Gerpe et al, 2000). However, the changes of MT mRNA in the testis were different from those in the liver of male mosquitofish exposed to steroid hormones.…”

“…Metallothionein (MT) is a low-molecular weight protein that is involved in the homeostasis of intracellular zinc and copper as well as detoxification of nonessential metals (Gerpe et al, 2000;Huang et al, 2011). Because induction of MT levels has frequently been associated with metal exposure, analysis of MT levels has been used as a biomarker of metal pollution in the aquatic environment.…”

“…Because induction of MT levels has frequently been associated with metal exposure, analysis of MT levels has been used as a biomarker of metal pollution in the aquatic environment. However, MT expression has been evidenced to be affected by certain hormones or (xeno)estrogens (Gerpe et al, 2000;Rhee et al, 2009). Nevertheless, the effects of steroid hormones on MT in fish are still poorly understood.…”

Regulation of reproduction- and biomarker-related gene expression by sex steroids in the livers and ovaries of adult female western mosquitofish (Gambusia affinis)

“…E2 treatment resulted in a significant downregulation of MT mRNA expression in two tested tissues of female mosquitofish in the present study. In a previous study, Gerpe et al (2000) reported that MT mRNA expression was not affected in the liver when arctic char (Salvelinus alpinus) were exposed to E2 or mimic estrogens alone, but those compounds could inhibit Cdinduced MT mRNA expression in that tissue. Werner et al (2003) also reported that MT concentrations were significantly reduced in the livers of lake trout exposed to the high and medium concentrations of ethynylestradiol.…”

“…Because induction of MT levels has frequently been associated with metal exposure, analysis of MT levels has been used as a biomarker of metal pollution in the aquatic environment. However, MT gene expression was affected by metals (Rhee et al, 2009), chemicals stressors (Gerpe et al, 2000;Werner et al, 2003) and other factors including age, sex and tissue type (Rhee et al, 2009). Although MT genes have been cloned and their expression has been studied in a number of fish species in response to heavy metals, relatively little is known about how those genes are affected by natural or synthetic hormones (Gerpe et al, 2000;Werner et al, 2008;Rhee et al, 2009).…”