Abstract
Guppy (Poecilia reticulata) is an ideal model for studying environmental estrogens, and its large caudal fin has a high capacity to regenerate. This study analyzed the feasibility of caudal fin for detecting vitellogenin (Vtg), the most commonly used biomarker of environmental estrogens. Firstly, a sandwich ELISA for guppy Vtg was developed using purified lipovitellin and its antibody and it had a working range of 7.8–1000 ng/mL and detection limit of 3.1 ng/mL. The ELISA was used to detect tissue distribution of Vtg. In male guppy exposed to 50 and 100 ng/L 17β-estradiol (E2), Vtg concentration in caudal fin was higher than that in whole fish, brain, eyes, gonad, and skin, and was close to that in the liver. Furthermore, male guppies were exposed to environmental concentrations of 17a-ethinylestradiol (EE2) and bisphenol S (BPS) to validate the utility of caudal fin Vtg for detecting estrogenic activities. The lowest observed effect concentration of EE2 and BPS were lower than 2 ng/L and 1 μg/L, which were below or equal to the values reported for other species, demonstrating that caudal fin Vtg was highly sensitive to estrogenic chemicals. Therefore, caudal fins of guppies are suggested as alternative samples for Vtg biomarker detection.
Highlights
Environmental estrogens have aroused great concern worldwide owing to their adverse effects on wildlife health, including altered sex hormone levels[1], gonadal abnormalities, reduced fertility[2], and feminization of males[3]
Western blot elucidated that the polyclonal antibody raised against purified Lv reacted with whole-body homogenates (WBH) from E2-exposed male guppy, whereas no positive reaction occurred in control male WBH, indicating that the anti-Lv antibody was highly specific to guppy Vtg[25]
The sandwich ELISA developed using purified Lv and anti-Lv antibody had a working range of 7.8–1000 ng/mL and a detection limit of 3.1 ng/mL, which was consistent with the vaules reported for Vtg ELISA of tilapia (Sarotherodon melanotheron)[26] and rare minnow (Gobiocypris rarus)[27]
Summary
Environmental estrogens have aroused great concern worldwide owing to their adverse effects on wildlife health, including altered sex hormone levels[1], gonadal abnormalities, reduced fertility[2], and feminization of males[3]. Zhong et al.[12] reported that Vtg could be detected in various extrahepatic tissues of 17α-ethinylestradiol (EE2)-exposed male zebrafish (Danio rerio), and recommended skin and eye tissues as for Vtg analysis Sampling of these tissues would kill the fish, it was unable to measure Vtg induction at a later point in time. Vtg induction in the WBH, caudal fin, liver, brain, eye, gonad, and skin tissues of male guppy exposed to different concentrations of 17β-estradiol (E2) were measured by Western blot and the sandwich ELISA to evaluate the possibility of using caudal fin for Vtg detection. The reliability of Vtg in caudal fin as a biomarker of estrogenic contamination was validated by quantifying Vtg levels in WBH, liver, and caudal fin of male guppy exposed to environmental concentrations of two different exogenous estrogens, EE2 and bisphenol S (BPS), which are two commonly detected estrogenic chemicals in aquatic environments
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