Dynamics of estrogen biomarker responses in rainbow trout exposed to 17β‐estradiol and 17α‐ethinylestradiol

Abstract

We have investigated the response dynamics of the estrogen-dependent genes vitellogenin (VTG) and the vitelline envelope proteins (VEPs) as well as circulating VTG in immature female rainbow trout (Oncorhynchus mykiss) exposed to 17beta-estradiol (E2) and 17alpha-ethinylestradiol (EE2) for periods of 7 and 14 d. Gene responses were quantified by measurement of messenger RNA (mRNA) in liver extracts using a chemiluminescent hybridization protection assay. Circulating VTG was measured by a homologous enzyme-linked immunosorbent assay. Exposure to both E2 and EE2 induced concentration-dependent increases in all biomarkers. The data presented indicate that VEP genes may be more sensitive to estrogens than the VTG gene. The biomarker lowest-observed-effect concentrations (biomarkerLOEC) in the 14-d study with E2 were 14 ng/L (VTG protein, VTG mRNA, VEPbeta, and VEPgamma) or 4.8 ng/L (VEPalpha). The EE2 was 5- to 66-fold more potent depending on the biomarker studied. In the 7-d study, all biomarkers were elevated after 48-h exposure to E2, with biomarkerLOECs of 30 ng/L (VTG protein, VTG mRNA, and VEPgamma) or 9.7 ng/L (VEPalpha and VEPbeta). Vitellogenin mRNA was induced up to 1,000-fold above baseline, and this translated into an increase of approximately 50,000-fold in circulating VTG. In conclusion, all biomarkers responded to estrogen exposure at environmentally relevant concentrations.

Screening and Testing for Endocrine Disruption in Fish—Biomarkers As “Signposts,” Not “Traffic Lights,” in Risk Assessment

“…Assays for VTG are available for a wide range of fish species. Measurement of VTG mRNA has also been used recently for quantifying the potency of estrogens (Inui et al 2003; Larkin et al 2003; Thomas-Jones et al 2003), and its measurement has proved to be equally as effective in this capacity as the measurement of VTG protein (Folmar et al 2000; Hemmer et al 2002; Schmid et al 2002; Thomas-Jones et al 2003). Partial- or full-length VTG cDNAs have been cloned in 20 different species of fish [available from the National Center for Biotechnology Information (http://www.ncbi.nlm.nih.gov/)], thereby providing the potential for a wide application of the VTG transcript(s) as an estrogen biomarker.…”

“…VTG protein, in contrast with VTG mRNA, can be measured nondestructively in fish, which favors it for use in monitoring estrogen exposure in wild populations and for studies that require repetitive sampling from the same individual. Under maximal stimulation, the VTG protein also undergoes a level of induction up to a 1,000-fold higher than that with the VTG mRNA transcript (Thomas-Jones et al 2003). …”

“…In contrast, VEP mRNA can be measured with relative ease for the cloned sequences. VEP mRNAs have been shown to be responsive to estrogen exposure in several fish species (Arukwe et al 2000; Lee et al 2002; Thomas-Jones et al 2003). It should be noted that in the Arctic char ( Salvelinus fontinalis ), VTG and VEPs are not mediated via same mechanism because VEP induction can be regulated by cortisol in addition to estrogens (Berg et al 2004).…”

Oocyte zona pellucida proteins

“…Both Vtg and ZPs are transported in the circulatory system to the ovary of several teleost species, thus being readily detected in blood plasma. Although the regulation of ZP genes to a large extent is unknown, the ZPs have recently been implicated as sensitive biomarker of endocrine disruption in fish, for example swordfish, bluefin tuna, rainbow trout, and medaka (Desantis et al, 2005;Fossi et al, 2004;Thomas-Jones et al, 2003;Lee et al, 2002a, b).…”

Health risk characterisation for environmental pollutants with a new concept of overall risk probability

“…With effects assessment, the induction of significant level of vitellogenin (VTG), a yolk protein, has been commonly used as a biomarker for adverse health effects for fish. In this study, NOAEC values on VTG induction for fathead minnow, brown trout, rainbow trout, Japanese medaka, and zebrafish were derived from numerous published studies [1,53,54,[74][75][76][77][78][79][80][81][82][83][84][85][86][87].…”