Characterization of Iodothyronine Outer Ring and Inner Ring Deiodinase Activities in the Blue Tilapia,<i>Oreochromis Aureus</i>

Mol, K.; Geyten, Serge Van der; Darras, Veerle; Visser, Theo J.; Kühn, Eduard

doi:10.1210/endo.138.5.5130

Cited by 41 publications

(13 citation statements)

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“…This activation, as well a s the inactivation of thyroid hormones, occurs not in the thyroid, but in the periphery through the action of iodothyronine deiodinases (Eales & Brown 1993, Mol et al 1997. Although it has long been an issue of debate, recent molecular studies have indicated that in fish, as in mammals, at least three different selenocysteinecontaining deiodinases exist, with similar properties to their mammalian counterparts.…”

Section: Introductionmentioning

confidence: 99%

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus)

Geyten¹,

Byamungu²,

Reyns³

et al. 2005

Journal of Endocrinology

104

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Thyroid status is one of the most potent regulators of peripheral thyroid hormone metabolism in vertebrates. Despite this, the few papers that have been published concerning the role of thyroid hormones in the regulation of thyroid function in fish often offer conflicting data. We therefore set out to investigate the effects of tetraiodothyronine (thyroxine) (T 4 ) or tri-iodothyronine (T 3 ) supplementation (48 p.p.m.) via the food on plasma and tissue thyroid hormone levels as well as iodothyronine deiodinase (D) activities in the Nile tilapia (Oreochromis niloticus). T 4 supplementation did not induce a hyperthyroid state and subsequently had no effects on the thyroid hormone parameters measured, with the liver as the sole notable exception. In T 4 -fed tilapias, the hepatic T 4 levels increased substantially, and this was accompanied by an increase in in vitro type I deiodinase (D1) activity. Although the lack of effect of T 4 supplementation could be partially explained by an inefficient uptake of T 4 from the gut, our current data suggest that also the increased conversion of T 4 into reverse (r)T 3 by the D1 present in the liver plays an important role in this respect. In addition, T 3 supplementation increased plasma T 3 and decreased plasma T 4 concentrations. T 3 levels were also increased in the liver, brain, kidney, gill and white muscle, but without affecting local T 4 concentrations. However, this increase in T 3 availability remained without effect on D1 activity in liver and kidney. This observation, together with the 6-n-propylthiouracyl (PTU) insensitivity of the D1 enzyme in fish, sets the D1 in teleost fish clearly apart from its mammalian and avian counterparts. The changes in hepatic deiodinases confirm the role of the liver as an important T 3 -regulating tissue. However, the very short plasma half-life of exogenously administered T 3 implies the existence of an efficient T 3 clearing/degradation mechanism other than deiodination.

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Section: Introductionmentioning

confidence: 99%

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus)

Geyten¹,

Byamungu²,

Reyns³

et al. 2005

Journal of Endocrinology

104

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“…Mammalian D2 mRNA is mainly expressed in brain, pituitary, and brown adipose tissue but other human tissues including thyroid, skeletal muscle, and heart show D2 mRNA expression (Salvatore et al, 1996). In ®sh, the highest D2 activity is detected in liver (MacLatchy and Eales, 1992;Mol et al, 1997;Orozco et al, 1997). In mammals, D3 activity is found in brain, skin, placenta, and fetal tissues whereas in ®sh, high and low D3 activities are detected in brain and gill respectively (Mol et al, 1993;Mol et al, 1997;Mol et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

“…In ®sh, the highest D2 activity is detected in liver (MacLatchy and Eales, 1992;Mol et al, 1997;Orozco et al, 1997). In mammals, D3 activity is found in brain, skin, placenta, and fetal tissues whereas in ®sh, high and low D3 activities are detected in brain and gill respectively (Mol et al, 1993;Mol et al, 1997;Mol et al, 1998). Finally, in mammals, D1 activity is predominantly found in liver, kidney, and thyroid whereas in ®sh, the highest D1 activity is found in kidney.…”

Section: Introductionmentioning

confidence: 99%

“…Finally, in mammals, D1 activity is predominantly found in liver, kidney, and thyroid whereas in ®sh, the highest D1 activity is found in kidney. Fish D2 and D3 have similar biochemical properties compared to their mammalian counterpart (Mol et al, 1997). In contrast to mammalian D1, ®sh D1 that have been characterized to date, are less sensitive to inhibition by 6-propylthiouracil (PTU) (Sanders et al, 1997).…”

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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“…One fish species studied in detail in our lab is the tropical cyclid tilapia (Oreochromis aureus). 9 HPLC analysis of the degradation products after incubation of microsomes from different tilapian tissues with radiolabelled rT 3 , T 4 , or T 3 showed that ORD of rT 3 was mainly present in the kidney. ORD of T 4 was highest in liver and kidney, while in the brain T 4 was degraded entirely by IRD to rT 3 .…”

Section: Presence and Characterization Of Deiodinases In Nonmammalianmentioning

confidence: 98%

Control of Peripheral Thyroid Hormone Levels by Activating and Inactivating Deiodinases

Darras

Mol

Geyten

et al. 1998

Annals of the New York Academy of Sciences

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Characterization of Iodothyronine Outer Ring and Inner Ring Deiodinase Activities in the Blue Tilapia,Oreochromis Aureus

Cited by 41 publications

References 38 publications

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus)

Iodothyronine deiodinases and the control of plasma and tissue thyroid hormone levels in hyperthyroid tilapia (Oreochromis niloticus)

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

Control of Peripheral Thyroid Hormone Levels by Activating and Inactivating Deiodinases

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