The peripheral metabolism of thyroid hormones and regulation of thyroidal status in poikilotherms

Eales, J.G.

doi:10.1139/z85-183

Cited by 139 publications

(56 citation statements)

References 87 publications

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“…Thyroid hormones are stored bound to thyroglobulin in the follicular colloid. Hydrolysis of iodothyroglobulin in the epithelial cell layer liberates principally T 4 , which diffuses into the surrounding capillaries and rapidly partitions into lipid membranes (Dickson et al, 1987;Eales, 1985;Hillier, 1970). To counteract this effect and ensure an even distribution of thyroid hormones in perfused tissues (Mendel et al, 1987, Mendel andWeisiger, 1990), T 3 and T 4 are generally transported in the blood bound to serum proteins (Larsson et al, 1985;Robbins and Edelhoch, 1986).…”

Section: Thyroid Hormone-binding Proteinsmentioning

confidence: 99%

Evolution of the Thyroid Hormone-Binding Protein, Transthyretin

Power

Elias

Richardson

et al. 2000

General and Comparative Endocrinology

190

119

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Transthyretin (TTR) belongs to a group of proteins, which includes thyroxine-binding globulin and albumin, that bind to and transport thyroid hormones in the blood. TTR is also indirectly implicated in the carriage of vitamin A through the mediation of retinol-binding protein (RBP). It was first identified in 1942 in human serum and cerebrospinal fluid and was formerly called prealbumin for its ability to migrate faster than serum albumin on electrophoresis of whole plasma. It is a single polypeptide chain of 127 amino acids (14,000 Da) and is present in the plasma as a tetramer of noncovalently bound monomers. The major sites of synthesis of TTR in eutherian mammals, marsupials, and birds are the liver and choroid plexus but in reptiles it is synthesised only in the choroid plexus. The observation that TTR is strongly expressed in the choroid plexus but not in the liver of the stumpy-tailed lizard and the strong conservation of expression in the choroid plexus from reptiles to mammals have been taken as evidence to suggest that extrahepatic synthesis of TTR evolved first. The identification and cloning of TTR from the liver of an amphibian, Rana catesbeiana, and a teleost fish, Sparus aurata, and its absence from the choroid plexus of both species suggest an alternative model for its evolution. Protein modelling studies are presented that demonstrate differences in the electrostatic characteristics of the molecule in human, rat, chicken, and fish, which may explain why, in contrast to TTR from human and rat, TTR from fish and birds preferentially binds triiodo-L-thyronine.

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Section: Thyroid Hormone-binding Proteinsmentioning

confidence: 99%

Evolution of the Thyroid Hormone-Binding Protein, Transthyretin

Power

Elias

Richardson

et al. 2000

General and Comparative Endocrinology

190

119

View full text Add to dashboard Cite

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“…It is well known that thyroid hormones (TH) are required for normal development and growth in vertebrates (Barrington, 1975;Eales, 1985;Leatherland, 1987). In addition, speci®c receptors for iodothyronines have been identi®ed in nuclei of testicular and ovarian cells in ®sh and in mammals including humans suggesting that TH control the reproductive function (Jannini et al, 1990;Jana and Bhattacharya, 1993).…”

Section: Introductionmentioning

confidence: 99%

“…In addition, speci®c receptors for iodothyronines have been identi®ed in nuclei of testicular and ovarian cells in ®sh and in mammals including humans suggesting that TH control the reproductive function (Jannini et al, 1990;Jana and Bhattacharya, 1993). Mammalian and ®sh thyroid hormone receptors are highly homologous and show a similar preferential af®nity for T 3 as compared to other iodothyronines (Eales, 1985). However, the major secretion product of the thyroid follicles is not the biologically active T 3 but rather a prohormone termed thyroxine T 4 (Eales, 1985).…”

Section: Introductionmentioning

confidence: 99%

“…Mammalian and ®sh thyroid hormone receptors are highly homologous and show a similar preferential af®nity for T 3 as compared to other iodothyronines (Eales, 1985). However, the major secretion product of the thyroid follicles is not the biologically active T 3 but rather a prohormone termed thyroxine T 4 (Eales, 1985). This implies that circulating T 4 is activated by 5…”

Section: Introductionmentioning

confidence: 99%

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Type II iodothyronine deiodinase is preferentially expressed in rainbow trout (oncorhynchus mykiss) liver and gonads*

Sambroni

Gutieres

Cauty

et al. 2001

Molecular Reproduction Devel

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It is well admitted that thyroid hormones (TH) play a role in the development of vertebrates. The major secretory product of the thyroid is a pro-hormone, T(4), which is activated in peripheral tissues by outer ring deiodination to T(3). We have isolated from rainbow trout testis, a full length cDNA encoding type II iodothyronine deiodinase (rtD2). The cDNA was 2410 nucleotides long and coded for a polypeptide of 264 amino acids including a selenocysteine residue. The predicted molecular weight of rtD2 was 29.3 kDa and the isoelectric point 8.71. The deduced amino acids sequence showed 80% identity with Fundulus heteroclitus D2 (fhD2) but only 68-69% identity with rat, mouse, and human D2. The 3' UTR contained a putative selenocysteine insertion sequence (SECIS) similar to that described in human cDNA. The rtD2 gene was isolated and the gene structure was similar to that described in human with two exons separated by a large intron. We studied rtD2 gene expression by Northern blot analysis using total RNA extracted from testis, ovary, and other tissues. We found a high expression of a 3 kb transcript in liver and in gonads. A lower expression was also detected in posterior kidney. In testis, rtD2 mRNA expression was dependent on spermatogenic stages: it increased at the onset of spermatogenesis. Our results show that the structural characteristics of the D2 protein and gene have been highly conserved during evolution. The rtD2 mRNA expression in the gonads suggests that rtD2 may be a key factor regulating local supply of active T(3) during rainbow trout gametogenesis.

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“…Metamorphosis of leptocephalus conger eel coincides with a thyroid hormone surge (Yamano et al 1991). Thyroid hormone thyroxine (T 4 ) is secreted by thyroid follicle cells and converts to the biologically active form, triiodothyronine (T 3 ), by deiodination in the peripheral tissues (Eales 1985). T 3 action is mediated by the thyroid hormone receptors α and β, which belong to the nuclear receptor superfamily (Wu & Koenig 2000).…”

Section: Introductionmentioning

confidence: 99%

Thyroid hormones are necessary for teleostean otolith growth

Shiao¹,

Hwang²

2004

Mar. Ecol. Prog. Ser.

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Experiments were conducted to understand the effects of thyroid hormones and thiourea (TU) on otolith growth during metamorphosis of leptocephali. TU is an anti-thyroid hormone drug that inhibits the production of thyroxine (T 4 ) and triiodothyronine (T 3 ) in the thyroid tissue. Fully grown leptocephali of tarpon Megalops cyprinoides collected at the mouth of the Gong-Shy-Tyan Brook, N Taiwan, were immediately treated with 10 ppb T 3 and 300 ppm TU for the experimental period of 13 d. The newly grown otolith lengths measured from the maximum radius were 77.0 ± 12.0, 91.9 ± 7.2 and 47.9 ± 6.3 µm in the control, T 3 and TU groups, respectively. The newly grown otolith length of the T 3 group was significantly longer than those of the control and TU groups, and the control group had significantly larger length values than the TU group. The T 3 treatment stimulated otolith growth, increasing daily increments from 7 to 13 cm (control) to 9 to 16 µm (T 3 ) during the growth peak of metamorphosis. Maximum daily increments were only 6 to 10 µm in TU-treated tarpons. The otoliths of the fish treated with T 3 and TU had increments deposited daily. Otoliths of T 3 -treated and control fish grew throughout the experimental period, but otoliths of TU-treated fish stopped growth beginning on Day 6 to Day 9. These results suggest that thyroid hormones are essential for otolith growth, probably by regulating the expressions and functions of the otolith protein matrix and ion transporters in the saccular epithelium.

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The peripheral metabolism of thyroid hormones and regulation of thyroidal status in poikilotherms

Cited by 139 publications

References 87 publications

Evolution of the Thyroid Hormone-Binding Protein, Transthyretin

Evolution of the Thyroid Hormone-Binding Protein, Transthyretin

Type II iodothyronine deiodinase is preferentially expressed in rainbow trout (oncorhynchus mykiss) liver and gonads*

Thyroid hormones are necessary for teleostean otolith growth

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