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Sex Steroids and Weakly Electric Fish: A Model System for Activational Mechanisms of Hormone Action
Published in Akira Matsumoto, Sexual Differentiation of the Brain, 2017
One might suspect that a sexually dimorphic signal may be under the influence of sex steroids. Indeed, this is the case. Analysis of blood samples taken from Sternopygus in the field just prior to the onset of the breeding season show that while levels of testosterone (T) are similar in both sexes, males have higher levels (~1 to 5 ng/ml) of 11-ketotestosterone (11KT — the dominant piscine androgen) than females, which have vanishingly low levels.23 T levels are often similar in the two sexes of fish and high levels of 11KT are associated with the occurrence of sexually dimorphic coloration, secondary structures, and behaviors in males in many species.4 EOD frequency in male Sternopygus is inversely correlated with androgen levels both in field-captured specimens and in fish treated in the laboratory with human chorionic gonadotropin to induce androgen secretion.22,23 Thus, EOD frequency varies in a graded way with plasma androgen level.
Environmental Androgens and Antiandrogens: An Expanding Chemical Universe
Published in Rajesh K. Naz, Endocrine Disruptors, 2004
L. Earl Gray, Vickie Wilson, Tammy Stoker, Christy Lambright, Johnathan Furr, Nigel Noriega, Phillip Hartig, Mary Cardon, Mitch Rosen, Gerald Ankley, Andrew Hotchkiss, Edward F. Orlando, Louis J. Guillette, William R. Kelce
Some of the greatest concerns about the effects of trenbolone relate to its potential effects on terrestrial and aquatic ecosystems around these feedlots because they are likely to be contaminated with the highest levels of this chemical and its metabolites. In this regard, Ankley et al.36 studied the effects of the androgenic growth promoter 17-beta-trenbolone on fecundity and reproductive endocrinology of the fathead minnow (Pimephales promelas). A competitive binding study with the fathead minnow androgen receptor demonstrated that 17-beta-trenbolone had a higher affinity for the receptor than did testosterone. When male and female fish were exposed for 21 days to nominal concentrations of 17-beta-trenbolone ranging from 0.005 to 50 microg/L, treated pairs displayed reduced fecundity (lowest observed effect level = 0.05 microg/L versus the measured concentrations of 0.027 microg/L). Treated females developed nuptial tubercles, structures normally present only on the heads of mature males, and had reduced plasma steroid (testosterone and 17 beta-estradiol) and vitellogenin levels. The 17-beta-trenbolone also altered reproductive hormone levels in male fathead minnows at concentrations higher than those producing effects in females. Males exposed to 17-beta-trenbolone at 41 microg/L exhibited decreased plasma concentrations of 11-ketotestosterone and increased concentrations of 17 beta-estradiol and vitellogenin. It is worthy to note that the in vivo effects of 17 beta trenbolone on fecundity and female fathead minnow reproductive morphology and function occurred at concentrations equivalent to those that induced luciferase in MDA-KB2 cells in vitro,24 indicating that this in vivo fish assay is very sensitive to androgens. Ongoing studies in Dr. Ankley’s laboratory are measuring trenbolone and its metabolites from water in aquatic ecosystems that receive effluent from Concentrated Animal Feedlot Operations (CAFOs). Recently, the USDA and USEPA released guidelines for CAFO effluent but these guidelines did not include monitoring of hormonally active substances like trenbolone. Further research is needed to determine if EDCs in CAFO effluents disrupt endocrine function, fecundity, population levels, or ecosystem diversity.
Detection of anti-androgenic activity of chemicals in fish studies: a data review
Published in Critical Reviews in Toxicology, 2023
Grace H. Panter, Rebecca J. Brown, Alan Jones, Oliver Körner, Laurent Lagadic, Lennart Weltje
The evaluated anti-androgens were also able to inhibit AR transactivation activated by 11-ketotestosterone (11-KT) or 5α-dihydrotestosterone (DHT) in a number of species, O. latipes, Melanotaenia fluviatilis (rainbow fish) and G. aculeatus (Table 2). Inhibitory concentrations (IC50) for flutamide are available for the ARβ for all three species activated by 11-KT, with G. aculeatus being the most sensitive (2.25 µM) and O. latipes the least (12 µM). IC50 values differed slightly between the receptor subtypes, with the β and α receptors being more sensitive in M. fluviatilis and G. aculeatus, respectively. The transactivation data was not as closely associated with the Bioactivity Model anti-androgen score as the competitive binding data (Table 2).
Androgens in premenopausal women and women with premature ovarian insufficiency
Published in Climacteric, 2021
Androgens are C19 steroids important for both reproductive and non-reproductive health in women. Testosterone is generally considered the main circulating androgen in premenopausal women as it can act directly as an androgen or be aromatized to estradiol (E2) in target tissues, resulting in pleiotropic effects8. Approximately half of the testosterone that can be measured in the blood in premenopausal women comes from the ovaries9,10. The other half comes from pro-hormones (dehydroepiandrosterone [DHEA] and androstenedione, also called ‘pre-androgens’) secreted by both the ovaries and the adrenal glands. The total circulating androgen pool also includes the 11-oxygenated C19 steroids, such as 11-ketoandrostenedione and 11-ketotestosterone, which are of adrenal origin11. These have been shown to account for a considerable proportion of the circulating androgen pool12,13; however, their biologic activity remains uncertain14,15.
Effects of atrazine on fish, amphibians, and reptiles: update of the analysis based on quantitative weight of evidence
Published in Critical Reviews in Toxicology, 2019
Mark L. Hanson, Keith R. Solomon, Glen J. Van Der Kraak, Richard A. Brian
In the only one new study on 11-ketotestosterone (11-KT), there were no changes in the concentrations of 11-KT in the testis of adult male zebrafish that had previously exposed to atrazine at 0, 0.3, 3, and 30 µg/L from 1 through 72 h post fertilization (Wirbisky et al. 2016b) (Figure 20). This study reinforced the conclusion of the WoE that atrazine has little impact on levels of 11-KT in males (mean score for relevance was 0.24 ± SE 0.14 and for quality was 2.26 ± SE 0.14). As the combined mean score for relevance was <1, the null hypothesis of causality was not falsified.