Control of pituitary thyroid-stimulating hormone synthesis and secretion by thyroid hormones during Xenopus metamorphosis

Sternberg, Robin M.; Thoemke, Kara; Korte, Joseph J.; Moen, Scott M.; Olson, Jessica; Korte, Lisa; Tietge, Joseph E.; Degitz, Sigmund J.

doi:10.1016/j.ygcen.2011.06.020

Cited by 25 publications

(11 citation statements)

References 17 publications

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“…RNA extraction and qPCRs were conducted following methods that have been described previously for X. laevis NIS (Sternberg et al, 2011;Tietge et al, 2013), with additional information provided below for the X. laevis IYD qPCR assay. Total RNA was extracted from thyroid glands and other tissues following manufacturer's instructions for the RNeasy Plus Micro Kits (Qiagen, Germantown, MD), with RNA quality and concentration determined with a Nanodrop ND-1000 Spectrophotometer (Nanodrop Technologies, Thermo Fisher Scientific, Waltham, MA).…”

Section: Rna Extraction and Quantitative Real-time Reverse Transcription Pcrsmentioning

confidence: 99%

Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians

Olker

Haselman

Kosian

et al. 2018

Toxicological Sciences

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The enzyme iodotyrosine deiodinase (dehalogenase, IYD) catalyzes iodide recycling and promotes iodide retention in thyroid follicular cells. Loss of function or chemical inhibition of IYD reduces available iodide for thyroid hormone synthesis, which leads to hormone insufficiency in tissues and subsequent negative developmental consequences. IYD activity is especially critical under conditions of lower dietary iodine and in low iodine environments. Our objective was to evaluate the toxicological relevance of IYD inhibition in a model amphibian (Xenopus laevis) used extensively for thyroid disruption research. First, we characterized IYD ontogeny through quantification of IYD mRNA expression. Under normal development, IYD was expressed in thyroid glands, kidneys, liver, and intestines, but minimally in the tail. Then, we evaluated how IYD inhibition affected developing larval X. laevis with an in vivo exposure to a known IYD inhibitor (3-nitro-l-tyrosine, MNT) under iodine-controlled conditions; MNT concentrations were 7.4-200 mg/L, with an additional 'rescue' treatment of 200 mg/L MNT supplemented with iodide. Chemical inhibition of IYD resulted in markedly delayed development, with larvae in the highest MNT concentrations arrested prior to metamorphic climax. This effect was linked to reduced glandular and circulating thyroid hormones, increased thyroidal sodium-iodide symporter gene expression, and follicular cell hypertrophy and hyperplasia. Iodide supplementation negated these effects, effectively rescuing exposed larvae. These results establish toxicological relevance of IYD inhibition in amphibians. Given the highly conserved nature of the IYD protein sequence and scarcity of environmental iodine, IYD should be further investigated as a target for thyroid axis disruption in freshwater organisms.

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Section: Rna Extraction and Quantitative Real-time Reverse Transcription Pcrsmentioning

confidence: 99%

Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians

Olker

Haselman

Kosian

et al. 2018

Toxicological Sciences

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“…As obesity, blood glucose, blood lipid and BP are all features of MetS, it is hypothesized that THs are a useful predictive factor for developing MetS. On the other hand, thyroid‐stimulating hormone (TSH) binds to receptors on epithelial cells in the thyroid gland, stimulating synthesis and secretion of THs by negative feedback inhibition …”

Section: Introductionmentioning

confidence: 99%

The association between thyroid function and incidence of metabolic syndrome in euthyroid subjects: Tianjin chronic low‐grade systemic inflammation and health cohort study

Wang

Zhang

et al. 2018

Clinical Endocrinology

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“…The stimulus for both follicular cell hypertrophy and hyperplasia is increased circulating levels of thyroid-stimulating hormone (TSH) (Tietge et al, 2010), concentrations of which are highest in the X. laevis pituitary between NF stages 58 and 62 . Although not completely understood, the rapid elevation in TSH associated with metamorphic climax occurs despite a concomitant rise in circulating TH, which would otherwise be expected to suppress pituitary TSH production via the classic HPT negative feedback mechanism (Buckbinder and Brown, 1993;Sternberg et al, 2011). Following the completion of metamorphosis (e.g., NF stage 66), levels of TSH and TH decrease, at which point the histological appearance of the thyroid glands becomes more quiescent (Grim et al, 2009).…”

Section: Discussionmentioning

confidence: 99%

Effect of triclosan on anuran development and growth in a larval amphibian growth and development assay

et al. 2017

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A larval amphibian growth and development assay was performed to evaluate the potential effects of environmentally-relevant concentrations of triclosan (TCS) on amphibian development and growth. Xenopus laevis were exposed to TCS 0.0 (control), 6.3, 12.5 and 25.0 μg l (estimated maximum tolerable concentration) until 10 weeks post-metamorphosis. At median metamorphosis time (Nieuwkoop and Faber stage 62), five larvae per replicate were collected for snout-vent length, hind limb length and body weight measurements, and histopathological examination of thyroid glands. Endpoints evaluated at test termination were based on draft guidance (USEPA, ) and included: survival; snout-vent length; body weight; gender; nuptial pad development (males); and liver, kidney, gonad and gonadal ducts histopathology. Exposure to TCS did not decrease survival, induce general signs of toxicity, affect median metamorphosis time or alter sex ratios. Exposure to TCS 12.5 and 25 μg l increased growth during the metamorphic stages relative to the control, but did not influence growth during the post-metamorphic phase. Overall, several statistically significant findings were found in larvae exposed to TCS, such as a decrease in the prevalence of stage 3 Müllerian ducts in the anterior trunk sections of TCS 25.0 μg l dose group females as compared to controls; most were not considered toxicologically relevant. Copyright © 2017 John Wiley & Sons, Ltd.

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Control of pituitary thyroid-stimulating hormone synthesis and secretion by thyroid hormones during Xenopus metamorphosis

Cited by 25 publications

References 17 publications

Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians

Evaluating Iodide Recycling Inhibition as a Novel Molecular Initiating Event for Thyroid Axis Disruption in Amphibians

The association between thyroid function and incidence of metabolic syndrome in euthyroid subjects: Tianjin chronic low‐grade systemic inflammation and health cohort study

Effect of triclosan on anuran development and growth in a larval amphibian growth and development assay

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