Application of a new bioassay technique using goldfish for assessment of water toxicity

Responses of antioxidant and biotransformation enzymes in Carassius carassius exposed to hexabromocyclododecane

The ubiquitous existence of hexabromocyclododecane (HBCD) in environmental matrices has made it attractive to both field investigators as well as laboratory researchers. However, literature on the biological effects caused by HBCD on aquatic vertebrates seldom exist. This has inevitably increased the difficulty of toxicological assessment in the aquatic environment. Juvenile crucian carp (Carassius carassius) were exposed (flow-through) to different concentrations of technical HBCD (nominal 2, 20, 200 μg L^-1) for 7 days to determine the responses of antioxidant and biotransformation enzymes. HBCD was found to be increasingly bioconcentrated in the fish livers as time proceeds. Also, the contribution of α-HBCD exhibited an enhancement from 13% in the exposure solutions to 24% in crucian carp, still much lower than in wild fishes (ca. 80%). HBCD induced activities of antioxidant enzymes in most cases, as well as increased level of lipid peroxidation. In contrast to the weak response of 7-ethoxyresorufin-O-deethylase (EROD), 7-pentoxyresorufin-O-depentylase (PROD) activity was generally induced in a time-dependent manner with peaks at day 2. Phase II enzyme Glutathione-S-transferase (GST) showed a dose-dependent induction with maximums in the 20 μg L^-1 treatment at all the four timepoints of 1, 2, 4 and 7 days. Some enzymatic responses showed good associations, indicating coordinated functions. To sum up, tHBCD exposure in the present circumstance had produced an ecological stress to crucian carp. The low levels of biotransformation and slow rates of bioisomerization suggest a possible long-term toxic effect, especially around HBCD point sources.

Development of a lipovitellin-based sandwich ELISA for quantification of vitellogenin in surface mucus and plasma of goldfish (Carassius auratus)

Goldfish (Carassius auratus) vitellogenin (Vtg) is an efficient biomarker for estrogen contamination in aquatic environments. In this study, Vtg and lipovitellin (Lv) were purified from the plasma of 17β-estradiol (E2)-induced male goldfish and unfertilized eggs of females, and were used to generate polyclonal antibodies against Vtg (anti-Vtg) and Lv (anti-Lv), respectively. SDS-PAGE and Western blot were performed to confirm the specificity of the two antibodies and the immunological similarity between Vtg and Lv. As anti-Lv recognized more antigen epitopes than anti-Vtg, it was used to develop a sandwich enzyme-linked immunosorbent assay (ELISA) for goldfish Vtg with purified Lv as the standard. The detection limit of the assay was 1.82ng/mL, and the working range was 3.9-250ng/mL. The use of Lv instead of Vtg as the standard provided greater precision and strengthened the robustness of the sandwich ELISA. Western blot and the Lv-based ELISA were used to detect Vtg inductions in surface mucus and plasma of E2-induced goldfish. The surface mucus Vtg level in E2-induced males was significantly higher than that in the control males and E2-induced females, and was much closer to the plasma Vtg level in E2-induced males than that in E2-induced females. Therefore, the surface mucus Vtg level of male goldfish may be a reliable indicator of estrogenic activity in the aquatic environment.

Development of a lipovitellin-based goldfish (Carassius auratus) vitellogenin ELISA for detection of environmental estrogens

The susceptibility of vitellogenin (Vtg) to degradation is a major problem affecting the robustness of enzyme-linked immunosorbent assay (ELISA) for goldfish (Carassius auratus) Vtg. In this study, a phospholipoglycoprotein with molecular mass of ∼420kDa was purified from goldfish egg extracts and it produced a single band corresponding to ∼112kDa in SDS-polyacrylamide gel electrophoresis (SDS-PAGE). Additionally, the amino acid composition of the purified protein was comparable to that of lipovitellin (Lv) from other fish species. Thus, the purified protein was identified as goldfish Lv. Purified Lv and anti-Lv polyclonal antiserum were used to develop an ELISA with a detection range between 31.25 and 1000ngmL(-)(1). The intra- and inter-assay coefficients of variation were 6.45% and 7.08%, respectively. The immunological similarity between goldfish Vtg and Lv was confirmed by immunoelectrophoresis and Western blot. Goldfish Lv showed higher stability than Vtg after -80°C storage, multiple freeze/thaw cycles, and heat treatment. Moreover, the use of treated Lv in the ELISA did not change the slopes of standard curves. Parallelism between the Lv standard curve and plasma dilution curves of vitellogenic females confirmed the validity of the assay for quantifying plasma Vtg. The Lv-based Vtg ELISA was further applied to evaluate the estrogenic activity of monocrotophos pesticide.

Preparation of a polyclonal antibody against goldfish (Carassius auratus) vitellogenin and its application to detect the estrogenic effects of monocrotophos pesticide

Goldfish (Carassius auratus) represents a good model to detect the estrogenic effects of chemicals, and vitellogenin (Vtg) is a vital indicator of estrogenic activity. The heterologous anti-carp Vtg antibody has previously been used for goldfish Vtg detection. Here, we report the preparation of an anti-goldfish Vtg antibody to improve the sensitivity and specificity of goldfish Vtg immunoassays. Vtg was purified from the plasma of 17β-estradiol (E2)-induced goldfish by gel filtration followed by anion-exchange chromatography. It was characterized as a phospholipoglycoprotein with an apparent molecular weight of ~460 kDa and separated into three major polypeptides corresponding to ~130, ~106, and ~81 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). A polyclonal antibody against goldfish Vtg was raised in rabbits and found to be specific for goldfish Vtg through immunoelectrophoresis and Western blot. A sensitive sandwich enzyme-linked immunosorbent assay (ELISA) was developed for the quantification of plasma Vtg, with a detection limit of 3.6 ng/mL and a detection range from 7.8 to 250 ng/mL. The intra- and inter-assay coefficients of variations were 2.4-6.8% and 6.7-10.8%, respectively. Additionally, we qualitatively and quantitatively detected the induction of Vtg in male fish exposed to 0.01, 0.01, and 1.00 mg/L monocrotophos pesticide by Western blot and ELISA. The homologous sandwich ELISA based on the anti-goldfish Vtg antibody could provide a valuable tool for the study of estrogenic effects of exogenous chemicals on goldfish.

The antidepressant tranylcypromine alters cellular proliferation and migration in the adult goldfish brain

The goldfish (Carassius auratus) is a widely studied vertebrate model organism for studying cell proliferation in the adult brain, and provide the experimental advantage of growing their body and brain throughout their ∼30-year life time. Cell proliferation occurs in the teleost brain in widespread proliferation zones. Increased cell proliferation in the brain has been linked to the actions of certain antidepressants, including tranylcypromine (TCP), which is used in the treatment of depression. We hypothesized that proliferation zones in the adult goldfish brain can be used to determine the antidepressant effects on cellular proliferation. Here, we report that bromodeoxyuridine (BrdU) labeling over a 24-hr period can be used to rapidly identify the proliferation zones throughout the goldfish brain, including the telencephalon, diencephalon, optic tectal lobes, cerebellum, and facial and vagal lobes. In the first 24 hr of BrdU administration, TCP caused an approximate and significant doubling of labeled cells in the combined brain regions examined, as detected by BrdU immunohistochemistry. TCP caused the greatest increase in cell proliferation in the cerebellum. The normal migratory paths of the proliferating cells within the cerebellum were not affected by TCP treatment. These results indicate that the goldfish provide significant advantages as a vertebrate model for rapidly investigating the effects of antidepressant drugs on cellular proliferation and migration in the normal and injured brain.