Circadian Rhythms of Thyroid Secretion, Morphometry, and Cell Division in Prometamorphic and Climax Rana Tadpoles

Wright, Mary L.; Blanchard, Linda S.; Pikula, Agata; Labieniec, Kristina E.

doi:10.1006/gcen.1995.1087

Cited by 13 publications

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“…The influence of TSH is tonic but can be adjusted rapidly, almost on a minute-to-minute basis, by means of an altered concentration of the ligand. This in turn supports the notion that the pulsatile and circadian release of TSH from the pituitary (7,19) is likely transmitted to rapid changes in thyroid structure and function (19,37,43,44). In terms of altered electrolyte transport, there are several indications pointing to the possibility that this may have important physiological implications.…”

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confidence: 70%

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Deactivation of TSH receptor signaling in filter-cultured pig thyroid epithelial cells

Ericson

Nilsson

2000

American Journal of Physiology-Endocrinology and Metabolism

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Thyrotropin [thyroid-stimulating hormone (TSH)] receptor on-off signaling was studied in polarized monolayers of pig thyrocytes cultured on permeable support. Transepithelial resistance (R) and potential difference (PD) were used as parameters to monitor the effect of altered TSH concentrations on vectorial electrolyte transport. TSH induced rapid but long-lasting changes in R (decrease) and PD (increase) that were cAMP-dependent and related to enhanced transcellular conductance of sodium and chloride. Withdrawal of TSH from cultures prestimulated with TSH (0.1 mU/ml) for 48 h resulted in restitution of R to control level within 30 min. Such deactivation was markedly accelerated by mild trypsinization, which degraded receptor-bound ligand without affecting TSH receptor responsiveness or ion transporting capacity. Small alterations in the TSH concentration (0.01-0.1 mU/ml) were followed almost instantaneously by adjustments of R. In contrast, the reversal of R after acute TSH stimulation (30 min) and subsequent TSH washout was delayed for several hours independently of cell surface trypsinization. The observations indicate that, during continuous exposure to physiological concentrations, TSH exerts a close minute-to-minute surveillance of thyroid function and the rate-limiting step of deactivation is the dissociation of ligand from the TSH receptor at the cell surface. TSH-deprived cells briefly exposed to TSH are refractory to rapid deactivation, probably because of altered metabolism downstream of TSH receptor signal transduction.

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confidence: 70%

“…Knowledge in this respect is of significance to thyroid physiology. For instance, TSH secretion is circadian and pulsatile (7,19), and thyroid morphology varies during a 24-h period as a sign of changing TSH activity (19,37,43,44).…”

mentioning

confidence: 99%

Deactivation of TSH receptor signaling in filter-cultured pig thyroid epithelial cells

Ericson

Nilsson

2000

American Journal of Physiology-Endocrinology and Metabolism

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“…One possible explanation for these apparently contradictory results could be that T 4 administration at the moment of maximal endogenous hormone production would not induce a more potent effect, since the receptors would be mostly occupied by the endogenous hormone. Indeed, the same authors have recently found maximum in vitro T 4 secretion within a 4-hr interval beginning around the onset of dark in preclimax R. catesbeiana (Wright et al, 1995).…”

Section: Discussionmentioning

confidence: 80%

“…laevis: Burns et al, 1987), suggesting rhythmicity in the secretion of endogenous T 4 and/or in the receptor availability or even in peripheral deiodination since it is generally agreed that T 3 is the main bioactive hormone (Buscaglia et al, 1985). Indeed, a circadian rhythm of thyroid T 4 secretion occurs in prometamorphic and climax Rana tadpoles (Wright et al, 1995).…”

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confidence: 99%

Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Gancedo

Alonso-Gómez

Pedro

et al. 1997

General and Comparative Endocrinology

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“…Studies on thyroid system function during amphibian metamorphosis have so far been mainly concerned with the action of TH in peripheral tissues (Shi 1999), while knowledge about the thyroid gland function during metamorphic development is limited to the description of morphological and biochemical aspects of thyroid gland activity (Regard 1978, Wright et al 1995. Early studies in amphibians showed that, similar to mammals, treatment with mammalian TSH preparations leads to increased thyroidal iodide uptake (Lynn & Dent 1961, Hourdry & Regard 1975, whereas treatment with perchlorate and thiocyanate reduced thyroidal iodide uptake (Lynn & Dent 1960, Norris & Platt 1973.…”

Section: Introductionmentioning

confidence: 99%

Expression of sodium-iodide symporter mRNA in the thyroid gland of Xenopus laevis tadpoles: developmental expression, effects of antithyroidal compounds, and regulation by TSH

Opitz¹,

Trubiroha²,

Lorenz³

et al. 2006

Journal of Endocrinology

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The uptake of iodide represents the first step in thyroid hormone synthesis by thyroid follicular cells and is mediated by the sodium-iodide symporter (NIS). In mammals, expression of NIS is stimulated by TSH and transcription of the NIS gene involves regulation by the thyroid-specific transcription factors Pax8 and Nkx2$1. In this study, we examined the mRNA expression of NIS, Pax8 and Nkx2$1 in the thyroid gland of Xenopus laevis tadpoles by semiquantitative reverse transcriptase (RT)-PCR. During spontaneous metamorphosis, NIS mRNA expression was low in premetamorphic tadpoles, increased throughout prometamorphosis, and peaked at climax stage 60. Analysis of TSH bsubunit (TSHb) mRNA in the pituitary of the same tadpoles revealed a close temporal relationship in the expression of the two genes during metamorphosis, suggesting a regulatory role of TSH in the developmental expression of NIS. Treatment of tadpoles with goitrogenic compounds (sodium perchlorate and ethylenethiourea) increased TSHb mRNA expression (approximately twofold) and caused thyroid gland hyperplasia, confirming that feedback along the pituitary-thyroid axis was operative. Analysis of gene expression in the thyroid gland revealed that goitrogen treatment was correlated with increased expression of NIS mRNA (w20-fold). In the thyroid gland organ culture experiments, bovine TSH (bTSH; 1 mU/ml) strongly induced NIS mRNA expression. This effect was mimicked by co-culture of thyroid glands with pituitaries from stage 58 tadpoles and by agents that increase intracellular cAMP (forskolin, dibutyryl-cAMP). In addition, it could be shown that thyroid glands of X. laevis tadpoles express Pax8 and Nkx2$1 mRNA in a developmentally regulated manner and that ex vivo treatment of thyroid glands with bTSH, forskolin, and cAMP analogs increased the expression of Pax8 and Nkx2$1 mRNA. This is the first report on developmental profiles and hormonal regulation of thyroid gland gene expression in amphibian tadpoles and, together, results reveal a critical role of TSH in the regulation of NIS mRNA expression in the thyroid gland of X. laevis tadpoles.

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Circadian Rhythms of Thyroid Secretion, Morphometry, and Cell Division in Prometamorphic and Climax Rana Tadpoles

Cited by 13 publications

References 0 publications

Deactivation of TSH receptor signaling in filter-cultured pig thyroid epithelial cells

Deactivation of TSH receptor signaling in filter-cultured pig thyroid epithelial cells

Changes in Thyroid Hormone Concentrations and Total Contents through Ontogeny in Three Anuran Species: Evidence for Daily Cycles

Expression of sodium-iodide symporter mRNA in the thyroid gland of Xenopus laevis tadpoles: developmental expression, effects of antithyroidal compounds, and regulation by TSH

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