Interrelationships between thyroidal and reproductive endocrine systems in fish

Cyr, Daniel G.; Eales, J.G.

doi:10.1007/bf00182342

Cited by 186 publications

(143 citation statements)

References 193 publications

(165 reference statements)

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“…Particularly, in juvenile fish, where plasma estradiol levels can be very low (0.3 pmol/g tissue in juvenile steelhead trout; Yeoh et al 1996), an internal concentration of 5.6 g TBBPA/g lipid (approximately 0.4 nmol/g wet weight) could have some estrogenic influence. The fact that thyroid hormones are also crucial for the development in fish (Power et al 2001), and may act synergistically with gonadotropic hormones (Cyr and Eales 1996), hampers interpretation of the present results in mechanistic terms; however, in spite of tentative anti-thyroid effects of TBBPA in tadpoles (Kitamura et al 2005b), none of the findings in this study were consistent with the effects in zebrafish exposed to the anti-thyroid drug propylthiouracil in a partial life-cycle assay (Van der Ven et al 2006).…”

Section: Discussioncontrasting

confidence: 69%

“…Since sex steroids and thyroid hormones influence reproduction in aquatic vertebrates and may interact during larval development (Cyr and Eales 1996;Arcand-Hoy and Benson 1998), the presence of TBBPA in aquatic environments raises concern as to their possible impact on reproductive health in fish. Regarding endocrine effects of TBBPA in fish, the focus has been on the estrogen-dependent production of the yolk precursor vitellogenin (VTG), which was not affected by intraperitoneal exposure to TBBPA in rainbow trout and eelpout (Christiansen et al 2000;Ronisz et al 2004); however the combined effects of possible disruption of estrogen or thyroid hormonal systems on ecologically relevant parameters like reproduction and early life-stage development in fish exposed to TBBPA have not been taken into account.…”

Section: Introductionmentioning

confidence: 99%

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Toxicity of tetrabromobisphenol A (TBBPA) in zebrafish (Danio rerio) in a partial life-cycle test

et al. 2006

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Toxicological effects of the widely used flame retardant, tetrabromobisphenol A (TBBPA) were assessed in a partial life-cycle test with zebrafish (Danio rerio). Exposure of adult fish during 30 days to water-borne TBBPA in nominal concentrations ranging from 0 (control) to 1.5 M was followed by exposure of the offspring in early life stages up to 47 days posthatching (dph) to the same concentrations. Adults exposed to 3 and 6 M showed severe disorientation and lethargy shortly after beginning of exposure and were euthanized. Because semistatic exposure resulted in fluctuating water concentrations, pooled fish samples were chemically analyzed for internal dose assessment. Egg production was decreased in fish exposed to TBBPA concentrations of 0.047 M and higher, and a critical effect level of 7.2 g/g lipid with a lower 5% confidence limit of 3.9 g/g lipid for 50% decreased egg production was calculated. Histology of adult ovaries indicated a relative increase of premature oocytes in two surviving females exposed to 1.5 M. Hatching of TBBPA-exposed larvae was decreased except in animals exposed to 0.375 M. In the highest exposure concentration, early posthatching mortality was high (81%) in larvae and the surviving juveniles showed a significant predominance of the female phenotype. Exposure of eggs from control parents up to 6 M TBBPA resulted in increasing malformation and pericardial fluid accumulation from 1.5 M; at higher concentrations, all embryos failed to hatch. The presented results indicate decreased reproductive success in zebrafish at environmentally relevant TBBPA concentrations.

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Section: Discussioncontrasting

confidence: 69%

Section: Introductionmentioning

confidence: 99%

Toxicity of tetrabromobisphenol A (TBBPA) in zebrafish (Danio rerio) in a partial life-cycle test

et al. 2006

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“…Thyroid hormone is involved in the regulation of seasonal reproduction in fish. Positive correlations between various thyroidal indices and reproductive status have been reported in the majority of seasonally breeding teleosts, and thyroidal activity increases during early gonadal development 12 . In addition, radiothyroidectomy results in a major inhibition of testicular development, which can be rescued by thyroid hormone treatment 21 .…”

Section: Resultsmentioning

confidence: 90%

“…Furthermore, neither eyes nor the pineal organ, another photoreceptive organ in non-mammalian vertebrates, are necessary for the photoperiodic response in birds 9 ; instead, light received by the deep-brain photoreceptors induces expression of TSH in the PT 10 . Most fish living outside the tropics also exhibit a photoperiodic response 11 , and involvement of thyroid hormone in the regulation of seasonal reproduction has been described extensively 12 . However, fish do not possess an anatomically distinct PT, which is the regulatory hub of photoperiodism in birds and mammals.…”

mentioning

confidence: 99%

The saccus vasculosus of fish is a sensor of seasonal changes in day length

et al. 2013

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The pars tuberalis of the pituitary gland is the regulatory hub for seasonal reproduction in birds and mammals. Although fish also exhibit robust seasonal responses, they do not possess an anatomically distinct pars tuberalis. Here we report that the saccus vasculosus of fish is a seasonal sensor. We observe expression of key genes regulating seasonal reproduction and rhodopsin family genes in the saccus vasculosus of masu salmon. Immunohistochemical studies demonstrate that all of these genes are expressed in the coronet cells of the saccus vasculosus, suggesting the existence of a photoperiodic signalling pathway from light input to neuroendocrine output. In addition, isolated saccus vasculosus has the capacity to respond to photoperiodic signals, and its removal abolishes photoperiodic response of the gonad. Although the physiological role of the saccus vasculosus has been a mystery for several centuries, our findings indicate that the saccus vasculosus acts as a sensor of seasonal changes in day length in fish.

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“…Measures of thyrocyte height, an index of hypertrophy, did not yield statistical site differences, but values were smallest at LV (Table 4). Although the thyroid endocrine system plays a role in gonadal development and reproduction of teleosts (Cyr and Eales, 1996), the effects of thyroid endocrine disruption on reproductive fitness have been difficult to document (Brown et al, 2004;Carr and Patiño, 2011). Recent studies with zebrafish have indicated a relationship between the status of the thyroid endocrine system and gonadal sex differentiation, pubertal development, and reproduction Sharma and Patiño, 2013).…”

Section: Vtg and Thyroid Parametersmentioning

confidence: 99%