Effects of a model androgen (methyl testosterone) and a model anti-androgen (cyproterone acetate) on reproductive endocrine endpoints in a short-term adult mummichog (Fundulus heteroclitus) bioassay (original) (raw)
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Aquatic Toxicology, 2005
We tested the hypothesis that gross morphological abnormalities are a sensitive indicator of exposure to waterborne androgenic and anti-androgenic compounds during embryonic, larval and juvenile stages of development in the common estuarine killifish, the mummichog (Fundulus heteroclitus; Pisces: Cyprinodontidae). Static exposures with daily renewal were carried out with 10-100,000 ng/L of the androgen agonist, 17␣-methyltestosterone (MT), or the androgen antagonist, cyproterone acetate (CA), for 60 days post-fertilization (PF) in duplicate exposures. Measured concentrations were 78.4-155.8% of nominal concentrations for MT and 13.5-168.1% for CA. No dose-related or consistent effects of MT or CA were observed before hatch. In 60 days PF juveniles, incidence of skeletal abnormalities (scoliosis, lordosis, head, facial and fin), soft tissue abnormality (anal swelling) and hemorrhaging were significantly increased by MT but only at high concentrations (≥1000 ng/L). The 10,000 and 100,000 ng/L concentrations of MT produced a wider range of abnormalities than 1000 ng/L. Over 90% of fish exposed to 10,000 or 100,000 ng/L were abnormal with an average of over 3.5 abnormalities per fish. CA did not increase the incidence of any type of abnormality. Survival of juveniles to the end of the exposure was reduced by MT at concentrations of 1000 ng/L and greater in the first experiment and at concentrations of 10,000 ng/L and greater in the second experiment. Juvenile length was reduced by high concentrations of MT (≥10,000 ng/L) in the first experiment and by most concentrations in the second experiment. We conclude that morphological abnormalities in early-life stages of mummichogs are not a sensitive indicator of exposure to androgenic or anti-androgenic waterborne EDSs at environmentally relevant concentrations. Crown
General and Comparative Endocrinology, 2020
The environmental estrogen 17α-ethinylestradiol (EE 2) will depress or completely inhibit egg production in many common model teleosts at low concentrations (≤0.5 ng/L; Runnalls et al., 2015). This inhibition is not seen in the estuarine killifish, or mummichog (Fundulus heteroclitus), even when exposed to 100 ng/L EE 2. This relative insensitivity to EE 2 exposure indicates species-specific mechanisms for compensating for exogenous estrogenic exposure. This review compares various reproductive responses elicited by EE 2 in mummichog to other common model teleosts, such as zebrafish (Danio rerio) and fathead minnow (Pimephales promelas), identifying key endpoints where mummichog differ from other studied fish. For example, EE 2 accumulates primarily in the liver/gall bladder of mummichog, which is different than zebrafish and fathead minnow in which accumulation is predominantly in the carcass. Despite causing species-specific differences in fecundity, EE 2 has been shown to consistently induce hepatic vitellogenin in males and cause feminization/sex reversal during gonadal differentiation in larval mummichog, similar to other species. In addition, while gonadal steroidogenesis and plasma steroid levels respond to exogenous EE 2, it is generally at higher concentrations than observed in other species. In mummichog, production of 17β-estradiol (E 2) by full grown ovarian follicles remains high; unlike other teleost models where E 2 synthesis decreases as 17α,20β-dihydroxy-4-prenen-3-on levels increase to induce oocyte maturation. New evidence in mummichog indicates some dissimilarity in gonadal steroidogenic gene expression responses compared to gene expression responses in zebrafish and fathead minnow exposed to EE 2. The role of ovarian physiology continues to warrant investigation regarding the tolerance of mummichog to exogenous EE 2 exposure. Here we present a comprehensive review, highlighting key biological differences in response to EE 2 exposure between mummichog and other commonly used model teleosts.
Aquatic Toxicology, 2007
A short-term reproductive bioassay with the mummichog (Fundulus heteroclitus) was developed to link changes in endocrine status to reproductive potential subsequent to endocrine disrupting substance (EDS) exposure. Sexually mature mummichog were separated by sex and exposed to the synthetic estrogen 17␣-ethynylestradiol (EE 2 ) at nominal concentrations of 0-100 ng/L for 21 days using a static daily renewal protocol. Half of the fish were sampled on Day 21. At 100 ng/L, male fish had induction of vitellogenin (VTG), increased gonadosomatic index (GSI), decreased testosterone production and decreased circulating 11-ketotestosterone (11-KT). Female fish had decreased circulating estradiol (E 2 ) and testosterone (T) at 100 ng/L. There were some impacts at lower concentrations of EE 2 in both sexes, though the results were not consistent. On Day 21, the remaining male and female fish were combined at each treatment and exposed for an additional 7 days during which spawning and fertilization success were also assessed. Males exposed to 100 ng/L EE 2 exhibited VTG induction, increased GSI, and decreased T production on Day 28. Female fish had increased E 2 and T production at 1 and/or 10 ng/L and circulating E 2 levels remained depressed above 10 ng/L. Female fish exposed to 100 ng/L spawned fewer eggs; fertilization was also impaired. In a parallel exposure, measured EE 2 water concentrations were approximately 10-20% of nominal for the 100 ng/L EE 2 treatment over a 24-h static exposure; levels in the other treatments were below detectable levels. Fish exposed to nominal concentrations of EE 2 below environmentally relevant levels (i.e., <10 ng/L) showed minimal effects while both the endocrine system and reproductive potential were affected at 100 ng/L EE 2 (nominal).
The 21-day androgenised female stickleback endocrine screening assay
2009
1 2 Executive summary 1. The current OECD test guidelines for screening chemicals with potential endocrine 3 disrupting activity (TG 229 and TG 230) cannot clearly identify androgen antagonists due 4 to the lack of a suitable end-point in the 3 core species involved, the fathead minnow, the 5 medaka and the zebrafish. 6 2. The reported antiandrogenic activity in the aquatic environment based on the Yeast 7 Androgen Screen (YAS), a suitable in vitro test, is substantial. The evidence of high levels 8 of antiandrogens in the environment emphasises the need to develop a suitable assay for 9 chemical screening. 10 3. The 3-spined stickleback posses a unique trait, the presence of an androgen regulated 11 protein in their kidney, spiggin, which can be deployed in the detection of environmental 12 androgens and antiandrogens. 13 4. There are two in vivo tests using the stickleback that have the potential to identify 14 compounds with antiandrogenic activity, the stickleback-breeding test and the 15 androgenised female stickleback screen. 16 5. The design of the androgenised female stickleback screen (AFSS) is better suited as an 17 endocrine screen due to its simplicity and reproducibility in any laboratory. The fish are 18 simultaneously treated with a model androgen (dihydro-testosterone, DHT) at 5g/L and a 19 range of concentrations of the putative antiandrogen. Any antiandrogenic activity is 20 detected by the degree of reduction/inhibition of spiggin induction by the DHT treatment. 21 6. This report also addresses a retrospective validation of a large dataset using the AFSS 22 collaboration with Japanese co-workers (Nagae et al, 2007) but more methods are coming 87 to light (Hogan et al, 2009). 88 15. The bulk of the existing data were produced during the course of the EU-funded project 89 Endocrine disrupters: exploring novel endpoints, exposure, low-dose-and mixture-effects in 90 humans, aquatic wildlife and laboratory animals (EDEN), that was particularly focusing on 91 the effects of chemical mixtures. A sub-set of the data for exposures to single chemicals 92 rather than mixtures has been analysed in this report. 93 16. The second milestone was to undertake independent statistical analysis of the existing 94 data to assess whether or not the main end-point of the assay (kidney spiggin levels) has the 95 3 17. In support of the third milestone we generated of a small set of data anticipated as 99 essential for the validation process under the OECD guidelines. These data were focused 100 on two separate items: 101 To investigate the effect of carrier solvent on the end-point employed by the assay. The 102 OECD guideline for the fish screen explicitly states that the use of solvent should be avoided all together and if it absolutely necessary to employ a solvent for the in vivo exposures then the level of solvent should not exceed 0.01% at the fish aquaria. However all existing data employed methanol as a carrier solvent for administering the chemicals to the experimental aquaria reaching a final concentration of 0.1%. 103 104 105 106 107 109 110 111 119 120 Investigate the effect of a non-endocrine active substance on the end-point employed by 108 the assay. Currently the OECD guideline suggests that either potassium permanganate and/or n-Octanol are suitable negative control substances. We investigated the suitability of potassium permanganate (PP) for this purpose.