Heterogeneous Forms of Thyroid-Stimulating Hormone in Mouse Thyrotropic Tumor and Serum: Differences in Receptor-Binding and Adenylate Cyclase-Stimulating Activity

Pekonen, Fredrika; Carayon, Pierre; Amr, Sania; Bd, Weintraub

doi:10.1055/s-2007-1019354

Cited by 26 publications

(2 citation statements)

References 7 publications

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“…In contrast to the gonadotrophins, little information is available concerning the relationship between TSH polymorphism and bio¬ logical activity, although some studies suggest a relationship between TSH isohormones, carbohy¬ drate composition and bioactivity. For example, heterogeneous forms of TSH, observed in mouse thyrotrophic tumour and serum, and which differed only in carbohydrate composition, were found to have different biological activities (Pekonen et al 1981). In a recent report, glycosylation of the a subunit but not that of the ß subunit was shown to be essential for expression of the domains involved in TSH immunoreactivity, as well as those controlling the bioactivity of the hormone ).…”

Section: Discussionmentioning

confidence: 95%

Microheterogeneity of thyroid-stimulating hormone from the pituitaries of euthyroid, hypothyroid and hyperthyroid rats

Pickles

Peers²,

Robertson³

et al. 1992

Journal of Molecular Endocrinology

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The microheterogeneity of pituitary thyroid-stimulating hormone (TSH) is dependent on variations in the hormone's carbohydrate moieties. In this study, changes in the pattern of heterogeneity have been assessed by chromatofocusing, which separates the isospecies on the basis of their isoelectric points (pI). Rats (n = 6 per group) were either untreated or rendered hypo- or hyperthyroid by including in the drinking water either propylthiouracil (0.05% for 8 weeks) or thyroxine (T4; 4 mg/l for 6 weeks) before they were killed at 16 weeks. On autopsy, serum TSH and total T4 were (means +/- S.E.M.): 2 +/- 0.3 micrograms TSH/l and 64 +/- 5 nmol T4/l (control); < 1 microgram TSH/l and 133 +/- 6 nmol T4/l (hyperthyroid); 58 +/- 6 micrograms TSH/l and 32 +/- 6 nmol T4/l (hypothyroid). The pituitaries were individually homogenized and the TSH isoforms separated by chromatofocusing over a pH range of 7-4. Fractions were assayed for TSH by radioimmunoassay. TSH from the control group was distributed into seven major peaks with pI values of (means +/- S.E.M., n = 6) 6.9 +/- 0.1, 6.6 +/- 0.1, 6.2 +/- 0.1, 5.8 +/- 0.1, 5.5 +/- 0.1, 5.2 +/- 0.1 and 4.8 +/- 0.1; 7 +/- 3% of the TSH had a pI of < 4.0. Six peaks of TSH were conserved in the hypothyroid group (with pI values of 6.8 +/- 0.1, 6.5 +/- 0.1, 6.2 +/- 0.1, 5.8 +/- 0.1, 5.4 +/- 0.1 and 5.2 +/- 0.1), and 11 +/- 4% of the hormone had a pI of < 4.0.(ABSTRACT TRUNCATED AT 250 WORDS)

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Section: Discussionmentioning

confidence: 95%

Microheterogeneity of thyroid-stimulating hormone from the pituitaries of euthyroid, hypothyroid and hyperthyroid rats

Pickles

Peers²,

Robertson³

et al. 1992

Journal of Molecular Endocrinology

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“…The main positive regulator of TSH release is hypothalamic TRH (20), which activates the G q/11 -coupled TRH receptor-1 (TRHR1), also expressed in lactotrophs and a fraction of somatotrophs (21,22). TRH not only stimulates the release of prestored TSH and accounts for pulsatile and circadian patterns of TSH secretion but also stimulates Cga, Tshb, and Trhr expression and contributes to the posttranslational maturation of the TSH oligosaccharide chains, which guarantee the full biological activity of TSH (23)(24)(25)(26)(27)(28). However, the mechanism by which TRH/TRHR1 controls transcription has not been fully characterized (29 -32).…”

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confidence: 99%

Loss of Basal and TRH-StimulatedTshbExpression in Dispersed Pituitary Cells

et al. 2015

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This study addresses the in vivo and in vitro expression pattern of three genes that are operative in the thyrotroph subpopulation of anterior pituitary cells: glycoprotein α-chain (Cga), thyroid-stimulating hormone β-chain (Tshb), and TRH receptor (Trhr). In vivo, the expression of Cga and Tshb was robust, whereas the expression of Trhr was low. In cultured pituitary cells, there was a progressive decline in the expression of Cga, Tshb, and Trhr. The expression of Tshb could not be reversed via pulsatile or continuous TRH application in variable concentrations and treatment duration or by the removal of thyroid and steroid hormones from the sera. In parallel, the expression of CGA and TSHB proteins declined progressively in pituitary cells from both sexes. The lack of the effect of TRH on Tshb expression was not related to the age of pituitary cultures and the presence of functional TRH receptors. In cultured pituitary fragments, there was also a rapid decline in expression of these genes, but TRH was able to induce transient Tshb expression. In vivo, thyrotrophs were often in close proximity to each other and to somatotroph and folliculostellate cell networks and especially to the lactotroph cell network; such an organization pattern was lost in vitro. These observations suggest that the lack of influence of anterior pituitary architecture and/or intrapituitary factors probably accounts for the loss of basal and TRH-stimulated Tshb expression in dispersed pituitary cells.

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Hypothalamus‐Pituitary‐Thyroid Axis

Ortiga-Carvalho

Chiamolera

Pazos‐Moura

et al. 2016

Comprehensive Physiology

336

222

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The hypothalamus-pituitary-thyroid (HPT) axis determines the set point of thyroid hormone (TH) production. Hypothalamic thyrotropin-releasing hormone (TRH) stimulates the synthesis and secretion of pituitary thyrotropin (thyroid-stimulating hormone, TSH), which acts at the thyroid to stimulate all steps of TH biosynthesis and secretion. The THs thyroxine (T4) and triiodothyronine (T3) control the secretion of TRH and TSH by negative feedback to maintain physiological levels of the main hormones of the HPT axis. Reduction of circulating TH levels due to primary thyroid failure results in increased TRH and TSH production, whereas the opposite occurs when circulating THs are in excess. Other neural, humoral, and local factors modulate the HPT axis and, in specific situations, determine alterations in the physiological function of the axis. The roles of THs are vital to nervous system development, linear growth, energetic metabolism, and thermogenesis. THs also regulate the hepatic metabolism of nutrients, fluid balance and the cardiovascular system. In cells, TH actions are mediated mainly by nuclear TH receptors (210), which modify gene expression. T3 is the preferred ligand of THR, whereas T4, the serum concentration of which is 100-fold higher than that of T3, undergoes extra-thyroidal conversion to T3. This conversion is catalyzed by 5'-deiodinases (D1 and D2), which are TH-activating enzymes. T4 can also be inactivated by conversion to reverse T3, which has very low affinity for THR, by 5-deiodinase (D3). The regulation of deiodinases, particularly D2, and TH transporters at the cell membrane control T3 availability, which is fundamental for TH action. © 2016 American Physiological Society. Compr Physiol 6:1387-1428, 2016.

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Heterogeneous Forms of Thyroid-Stimulating Hormone in Mouse Thyrotropic Tumor and Serum: Differences in Receptor-Binding and Adenylate Cyclase-Stimulating Activity

Cited by 26 publications

References 7 publications

Microheterogeneity of thyroid-stimulating hormone from the pituitaries of euthyroid, hypothyroid and hyperthyroid rats

Microheterogeneity of thyroid-stimulating hormone from the pituitaries of euthyroid, hypothyroid and hyperthyroid rats

Loss of Basal and TRH-StimulatedTshbExpression in Dispersed Pituitary Cells

Hypothalamus‐Pituitary‐Thyroid Axis

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