Augmentation of nuclear binding capacity for triiodothyronine by aldosterone in tadpole tail.

Niki, Kaoru; Yoshizato, K.; Kikuyama, Sakaé

doi:10.2183/pjab.57.271

Cited by 31 publications

(13 citation statements)

References 6 publications

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“…Retardation of T4-induced metamorphosis by the Amphenone treatment and its recovery by the corticoid administration as observed in the present experiments, strongly suggest that endogenous corticoids play a role in accelerating metamorphosis. As to the mechanism of action of corticoids, it is postulated that the steroids elevate the tissue sensitivity to thyroid hormone by augmenting the nuclear binding capacity for thyroid hormone (Niki et al, 1981;Kikuyama et al, 1982a).…”

Section: Resultsmentioning

confidence: 99%

Retardation of thyroxine-induced metamorphosis by amphenone B in toad tadpoles.

et al. 1982

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The effect of Amphenone B, an inhibitor of corticoid synthesis, on thyroxine (T4)-induced metamorphosis was studied in toad tadpoles kept in thiourea.Amphenone injections retarded T4-induced tail resorption markedly. The effect of Amphenone was nullified by aldosterone and corticosterone added to the water in which tadpoles were kept. Steroidogenic cells of adrenals in Amphenone-injected animals were enlarged markedly as compared with those in the saline-injected tadpoles or the Amphenone-injected tadpoles which were supplemented with corticoids. The results strongly suggest that endogenous corticoids act together with thyroid hormone to accelerate metamorphosis.

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Section: Resultsmentioning

confidence: 99%

Retardation of thyroxine-induced metamorphosis by amphenone B in toad tadpoles.

et al. 1982

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“…CORT regulation of TR Positive regulation of TR expression by GR is implied by the finding that corticosteroids enhance nuclear T 3 binding capacity in tadpole tail (Niki et al 1981, Suzuki & Kikuyama 1983a). This effect of corticosteroids has been proposed as one mechanism whereby corticosteroids synergize with thyroid hormone to promote morphogenesis (Kikuyama et al 1993).…”

Section: Crossregulation Of Nuclear Hormone Receptorsmentioning

confidence: 99%

“…Several investigators have shown that corticosteroids can synergize with thyroid hormone to accelerate tadpole metamorphosis (see Kikuyama et al 1993, Hayes 1997 and at least two mechanisms have been proposed for this effect. For example, treatment with corticosteroids increases nuclear 3,5,3 -triiodothyronine (T 3 ) binding capacity in tailfin of two anuran species (Niki et al 1981, Suzuki & Kikuyama 1983b. Another mode of action may be through the regulation of tissue deiodinases, where corticosteroids can enhance conversion of thyroxine (T 4 ) to T 3 , the more biologically active hormone, and decrease the degradation of T 3 (Galton 1990).…”

Section: Introductionmentioning

confidence: 99%

Developmental expression and hormonal regulation of glucocorticoid and thyroid hormone receptors during metamorphosis in Xenopus laevis

Krain¹,

Denver²

2004

Journal of Endocrinology

102

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Corticosteroids, the primary circulating vertebrate stress hormones, are known to potentiate the actions of thyroid hormone in amphibian metamorphosis. Environmental modulation of the production of stress hormones may be one way that tadpoles respond to variation in their larval habitat, and thus control the timing of metamorphosis. Thyroid hormone and corticosteroids act through structurally similar nuclear receptors, and interactions at the transcriptional level could lead to regulation of common pathways controlling metamorphosis. To better understand the roles of corticosteroids in amphibian metamorphosis we analyzed the developmental and hormonedependent expression of glucocorticoid receptor (GR) mRNA in the brain (diencephalon), intestine and tail of Xenopus laevis tadpoles. We compared the expression patterns of GR with expression of thyroid hormone receptor beta (TR ). In an effort to determine the relationship between nuclear hormone receptor expression and levels of ligand, we also analyzed changes in wholebody content of 3,5,3 -triiodothyronine (T 3 ), thyroxine, and corticosterone (CORT). GR transcripts of 8, 4 and 2 kb were detected in all tadpole tissues, but only the 4 and 2 kb transcripts could be detected in embryos. The level of GR mRNA was low during premetamorphosis in the brain but increased significantly during prometamorphosis, remained at a constant level throughout metamorphosis, and increased to its highest level in the juvenile frog. GR mRNA level in the intestine remained relatively constant, but increased in the tail throughout metamorphosis, reaching a maximum at metamorphic climax. The level of GR mRNA was increased by treatment with CORT in the intestine but not in the brain or tail. TR mRNA level increased in the brain, intestine and tail during metamorphosis and was induced by treatment with T 3 . Analysis of possible crossregulatory relationships between GRs and TRs showed that GR mRNA was upregulated by exogenous T 3 (50 nM) in the tail but downregulated in the brain of premetamorphic tadpoles. Exogenous CORT (100 nM) upregulated TR mRNA in the intestine. Our findings provide evidence for tissuespecific positive, negative and crossregulation of nuclear hormone receptors during metamorphosis of X. laevis. The synergy of CORT with T 3 on tadpole tail resorption may depend on the accelerated accumulation of GR transcripts in this tissue during metamorphosis, which may be driven by rising plasma thyroid hormone titers.

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“…It has been suggested that corticosteroids promote metamorphosis synergistically with thyroid hormone (Kikuyama et al 1983a, b), presumably by augmenting the binding capacity of thyroid hormone in organs such as like the tail fin (Niki et al 1981;Suzuki and Kikuyama 1983).…”

Section: Introductionmentioning

confidence: 99%

Immunocytochemical and morphometric study on the changes of TSH, PRL, GH and ACTH cells during the development of Bufo arenarum

Miranda

Paz

Dezi

et al. 1995

Cell and Tissue Research

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The development and dynamics of thyrotropin (TSH), adrenocorticotropic hormone (ACTH), prolactin (PRL), and growth hormone (GH) cells have been studied using immunocytochemical techniques and rabbit antisera, raised against the relevant human hormone, in the pars distalis of Bufo arenarum larvae at different stages of development. The four types of cells studied were identified in different zones of the pars distalis: TSH cells occurred mainly in the centro-ventral zone, ACTH cells in the rostral and dorsal zones, GH cells in the central and caudal zones, and PRL cells in the anterior two-thirds of the gland. This distribution pattern does not show significant changes with development. Morphometry and stereology were used to evaluate the changes observed in the volume of the pars distalis and the immunoreactive cells during development. The former increased during larval growth and decreased throughout the metamorphic climax. The results obtained on cell number, volume density, and total volume suggest that, during larval growth (pre-prometamorphosis) of B. arenarum, TSH, PRL, GH and ACTH cells show a proliferative period with storage of their hormones; a second period involving hormone release occurs at the metamorphic climax.

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Augmentation of nuclear binding capacity for triiodothyronine by aldosterone in tadpole tail.

Cited by 31 publications

References 6 publications

Retardation of thyroxine-induced metamorphosis by amphenone B in toad tadpoles.

Retardation of thyroxine-induced metamorphosis by amphenone B in toad tadpoles.

Developmental expression and hormonal regulation of glucocorticoid and thyroid hormone receptors during metamorphosis in Xenopus laevis

Immunocytochemical and morphometric study on the changes of TSH, PRL, GH and ACTH cells during the development of Bufo arenarum

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