Thyroid hormones during development of a marsupial, the tammar wallaby, Macropus eugenii

Janssens, P.A.; Grigg, J.A.; Dove, H.; Hulbert, A. J.

doi:10.1677/joe.0.1270427

Cited by 24 publications

(10 citation statements)

References 21 publications

(27 reference statements)

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“…By day 200 full pelage has developed and the young leaves the pouch for the first time (See (40) for review). During this time, the young have elevated levels of TH in their blood: total T4 levels reach a peak around day 180, before declining to adult levels (16). Thyroidectomized pouch young showed retarded growth, fur development and homeothermy (40).…”

Section: Discussionmentioning

confidence: 99%

“…We suggested that this T4 distributor protein could serve as an additional THDP in the blood of the pouch young before its thyroid gland becomes functional, when the young obtains TH from the mother's milk. During this time, the young has elevated levels of THs in its blood (16). This raised the question as to whether W-TBP was the marsupial homologue of eutherian TBG.…”

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confidence: 99%

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Developmentally regulated thyroid hormone distributor proteins in marsupials, a reptile, and fish

Richardson¹,

Monk²,

Shepherdley³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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Thyroid hormones are essential for vertebrate development. There is a characteristic rise in thyroid hormone levels in blood during critical periods of thyroid hormone-regulated development. Thyroid hormones are lipophilic compounds, which readily partition from an aqueous environment into a lipid environment. Thyroid hormone distributor proteins are required to ensure adequate distribution of thyroid hormones, throughout the aqueous environment of the blood, and to counteract the avid partitioning of thyroid hormones into the lipid environment of cell membranes. In human blood, these proteins are albumin, transthyretin and thyroxine-binding globulin. We analyzed the developmental profile of thyroid hormone distributor proteins in serum from a representative of each order of marsupials ( M. eugenii; S.crassicaudata), a reptile ( C. porosus), in two species of salmonoid fishes ( S. salar; O. tshawytsch), and throughout a calendar year for sea bream ( S. aurata). We demonstrated that during development, these animals have a thyroid hormone distributor protein present in their blood which is not present in the adult blood. At least in mammals, this additional protein has higher affinity for thyroid hormones than the thyroid hormone distributor proteins in the blood of the adult. In fish, reptile and polyprotodont marsupial, this protein was transthyretin. In a diprotodont marsupial, it was thyroxine-binding globulin. We propose an hypothesis that an augmented thyroid hormone distributor protein network contributes to the rise in total thyroid hormone levels in the blood during development.

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Section: Discussionmentioning

confidence: 99%

mentioning

confidence: 99%

Developmentally regulated thyroid hormone distributor proteins in marsupials, a reptile, and fish

Richardson¹,

Monk²,

Shepherdley³

et al. 2005

American Journal of Physiology-Regulatory, Integrative and Comp

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show abstract

“…A method described by Janssens et al (1990) was used to define the plasma profile of GH in pouch young in terms of a simple exponential decline equation. The statistical package PRISM (GraphPad Software, San Diego, CA, USA) was used to fit the equation using a non-linear, least squares method.…”

Section: Statisticsmentioning

confidence: 99%

Plasma growth hormone and growth hormone-binding protein during development in the marsupial brushtail possum (Trichosurus vulpecula)

Saunders

Gemmell²,

Waters³

et al. 2002

Journal of Endocrinology

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Plasma concentrations of growth hormone (GH) were measured in the brushtail possum (Trichosurus vulpecula) pouch young from 25 through to 198 days post-partum (n=71). GH concentrations were highest early in pouch life (around 100 ng/ml), and thereafter declined in an exponential fashion to reach adult concentrations (10·8 1·8 ng/ml; n=21) by approximately 121-145 days post-partum, one to two months before the young is weaned. Growth hormone-binding protein (GHBP), which has been shown to modify the cellular actions of GH in eutherian mammals, was identified for the first time in a marsupial. Based on size exclusion gel filtration, possum GHBP had an estimated molecular mass of ]65 kDa, similar to that identified in other mammalian species, and binding of 125 I-labelled human GH (hGH) was displaced by excess hGH (20 µg). An immunoprecipitation method, in which plasma GHBP was rendered polyethylene glycol precipitable with a monoclonal antibody to the rabbit GHBP/GH receptor (MAb 43) and labelled with 125 I-hGH, was used to quantitate plasma GHBP by Scatchard analysis in the developing (pooled plasma samples) and adult (individual animals) possums. Binding affinity (K a ) values in pouch young aged between 45 and 54 and 144 and 153 days post-partum varied between 1·0 and 2·4 10 9 /M, which was slightly higher than that in adult plasma (0·96 0·2 10 9 /M, n=6). Binding capacity (B max ) values increased from nondetectable levels in animals aged 25-38 days post-partum to reach concentrations around half that seen in the adult (1·4 0·2 10 -9 M) by about 117 days post-partum and remained at this level until 153 days post-partum. Therefore, in early pouch life when plasma GH concentrations are highest, the very low concentrations of GHBP are unlikely to be important in terms of competing with GH-receptor for ligand or altering the half-life of circulating GH.

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“…Thus, there is thyroidal involvement in normal growth of the tammar wallaby and turtles (429,828); in the control of food intake and energy usage in reptiles, birds, and fish (299,392,393,433,470); and in ovarian development and gestation in certain teleosts (497)(498)(499). These and other aspects of thyroidal endocrinology will be referred to again in later sections.…”

Section: Primary Structures Of Secretinmentioning

confidence: 99%

Endocrinology of the Vertebrates

Henderson

1997

Comprehensive Physiology

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Thyroid hormones during development of a marsupial, the tammar wallaby, Macropus eugenii

Cited by 24 publications

References 21 publications

Developmentally regulated thyroid hormone distributor proteins in marsupials, a reptile, and fish

Developmentally regulated thyroid hormone distributor proteins in marsupials, a reptile, and fish

Plasma growth hormone and growth hormone-binding protein during development in the marsupial brushtail possum (Trichosurus vulpecula)

Endocrinology of the Vertebrates

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