Light and Electron Microscopic Immunocytochemistry of TSH-like Cells Occurring in the Pars tuberalis of the Adult Male Rat Pituitary.

Sakai, Takafumi; Inoue, Kinji; Kurosumi, Kazumasa

doi:10.1679/aohc.55.151

Cited by 25 publications

(27 citation statements)

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“…However, the TSH secretion from the PT was significantly increased by the glutamic acid treatment, and this finding was consistent with the observed TSHb mRNA expression level. Most of the hormoneproducing cells in the rat PT are small and oval-shaped TSH-producing cells (Gross 1984) and are characterized by spot-like TSH immunoreactivity on the Golgi apparatus, with few secretory granules being found in the cytoplasm under electron microscopic observation (Sakai et al 1992), which suggests that TSH may be secreted constitutively from PT-TSH cells. In this study, spot-like TSH-immunoreactive staining of the Golgi apparatus was observed in all examined conditions (Fig.…”

Section: Discussionmentioning

confidence: 97%

“…The hormone-producing cells in the PT vary according to species (Gross 1984). In rats, most of the hormone-producing cells in the PT are small and oval-shaped TSH-producing cells (Gross 1984) and they are characterized by spot-like TSH immunoreactivity on the Golgi apparatus (Sakai et al 1992). TSH produced in the PT (PT-TSH) acts on the TSH receptors and regulates the expression of type 2 deiodinase (Dio2) in the ependymal cell layer of the mediobasal hypothalamus, which results in the regulation of GnRH release into the median eminence in seasonal animals (Yoshimura et al 2003, Watanabe et al 2004.…”

Section: Introductionmentioning

confidence: 99%

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Glutamine and glutamic acid enhance thyroid-stimulating hormone β subunit mRNA expression in the rat pars tuberalis

Aizawa¹,

Sakai²,

Sakata³

2012

Journal of Endocrinology

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Thyroid-stimulating hormone (TSH)-producing cells of the pars tuberalis (PT) display distinct characteristics that differ from those of the pars distalis (PD). The mRNA expression of TSHb and aGSU in PT has a circadian rhythm and is inhibited by melatonin via melatonin receptor type 1; however, the detailed regulatory mechanism for TSHb expression in the PT remains unclear. To identify the factors that affect PT, a microarray analysis was performed on lasercaptured PT tissue to screen for genes coding for receptors that are abundantly expressed in the PT. In the PT, we found high expression of the KA2, which is an ionotropic glutamic acid receptor (iGluR). In addition, the amino acid transporter A2 (ATA2), also known as the glutamine transporter, and glutaminase (GLS ), as well as GLS2, were highly expressed in the PT compared to the PD. We examined the effects of glutamine and glutamic acid on TSHb expression and aGSU expression in PT slice cultures. L-Glutamine and L-glutamic acid significantly stimulated TSHb expression in PT slices after 2-and 4-h treatments, and the effect of L-glutamic acid was stronger than that of L-glutamine. In contrast, treatment with glutamine and glutamic acid did not affect aGSU expression in the PT or the expression of TSHb or aGSU in the PD. These results strongly suggest that glutamine is taken up by PT cells through ATA2 and that glutamic acid locally converted from glutamine by Gls induces TSHb expression via the KA2 in an autocrine and/or paracrine manner in the PT.

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Section: Discussionmentioning

confidence: 97%

Section: Introductionmentioning

confidence: 99%

Glutamine and glutamic acid enhance thyroid-stimulating hormone β subunit mRNA expression in the rat pars tuberalis

Aizawa¹,

Sakai²,

Sakata³

2012

Journal of Endocrinology

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“…PT-specific cells of various rodent species have been shown to express β-thyrotropin hormone (TSH) and the common α-subunit of the PD glycoprotein hormone (GSU) [8,9,10,11,12]. The use of dual labeling to detect the MT1 melatonin receptor mRNA and pituitary hormones has led to the demonstration that in the PT of the rat and the European hamster, β-TSH-positive cells express the MT1 receptor [13,14].…”

Section: Introductionmentioning

confidence: 99%

“…In the rat PT, immunoreaction is very strong in a paranuclear spot [28]. Such a spot, revealed by other methods, had been regarded as a typical morphological marker of PT-specific cells [9,10,11]. …”

Section: Introductionmentioning

confidence: 99%

Expression of Tuberalin II, α-Subunit of Glycoprotein Hormones and β-Thyrotropin Hormone in the Pars Tuberalis of the Rat: Immunocytochemical Evidence for Pars Tuberalis-Specific Cell Types

Guerra

Rodríguez²

2009

Neuroendocrinology

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Increasing evidence suggests that the hypophyseal pars tuberalis (PT) plays a key role in the transduction of light/dark (melatonin) information to the endocrine system. It has been shown that PT-specific cells express melatonin receptors and thyrotropin hormone (TSH) subunits. However, these cells do not resemble thyrotrophs or any other of the pars distalis (PD) cells. There is evidence that PT-specific cells secrete a glycoprotein hormone designated as ‘tuberalin’. We have identified a putative tuberalin of 21 kDa (tuberalin II) and have raised antibodies against it. To further investigate whether tuberalin II is a distinct secretory compound of the PT, absorption studies of antituberalin II with TSH or with an extract of the rat PD containing β-TSH, β-luteinizing hormone (LH) and the common α-subunit of glycoprotein hormones (GSU), were performed. Neither of the absorption tests abolished the immunoreactivity of the PT to antituberalin II, suggesting that tuberalin II is different from TSH or the other PD glycoprotein hormones. Double immunofluorescence analyses using antibodies against tuberalin II, β-TSH and GSU revealed that in the developing and adult PT there are 3 populations of PT-specific cells expressing tuberalin II and GSU (type 1), β-TSH and GSU (type 2) and tuberalin II, β-TSH and GSU (type 3). This further indicates that tuberalin II and β-TSH correspond to different compounds and that they may be expressed either by different cells types or coexpressed in a 3rd cell type. The distribution and temporal expression of tuberalin II, β-TSH, β-LH and GSU were investigated in the developing pituitary gland. At E14.5, tuberalin II and GSU were expressed by cells of the PT primordium but not by the PD and pars intermedia primordia. The onset of expression of β-TSH, β-LH and GSU in cells of the PD occurred about 1 day later, further indicating the distinct nature of tuberalin II and supporting the earlier view that the secretion of polypeptides from the fetal rat pituitary gland begins in PT-specific cells.

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“…This pattern of gene expression combined with the absence of thyrotrope cells in the Snell dwarf mouse, which lacks functional Pit-1, led to the hypothesis that the rostral tip or Pit-1-independent thyrotropes are a transient population that does not persist in the adult (38). However, at least two populations of thyrotropes are found in the adult rodent pituitary: one population in the pars tuberalis and a second in the pars distalis (5,6). Although the Pit-1 dependence of the pars tuberalis population is not definitively established in rodents, the pars tuberalis and pars distalis thyrotropes can be distinguished by their sensitivities to thyroid hormone (7).…”

Section: Discussionmentioning

confidence: 99%

The Thyrotropin β-Subunit Gene Is Repressed by Thyroid Hormone in a Novel Thyrotrope Cell Line, Mouse TαT1 Cells**This work was supported by NIH Research Grants R01-HD-20377 and HD-12303 (to P.L.M.) and R01-DK-36843 (to E.C.R.); fellowships from the Spanish Ministry of Education and Science and Fundacion Jaime del Amo, Universidad Complutense de Madrid, Spain (to B.Y.); and a Ford Foundation Fellowship, the President’s Fellowship of the University of California, and NIH National Research Scientist Award Fe

Yusta

Et²,

Df³

et al. 1998

Endocrinology

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TSH is expressed in two populations of thyrotropes in the pituitary: one in the pars distalis and a second in the pars tuberalis. Pars distalis thyrotropes exhibit classical endocrine inhibition of TSH by thyroid hormone, whereas pars tuberalis thyrotropes do not. The majority of our understanding of TSH subunit gene regulation has come from studies conducted in dispersed pituitary, dispersed thyrotropic tumors, or the GH 3 somatolactotrope cell line. However, the dispersed pituitary model is limited because of its inherent heterogeneity, thyrotropic tumors are difficult to grow and maintain, and the GH 3 cells lack endogenous TSH expression. The recent derivation of a clonal thyrotrope cell line, T␣T1, that expresses thyrotrope-specific markers, overcomes these limitations. However, because it was not possible to distinguish whether the tumor from which the T␣T1 cells are derived originated in the pars distalis or the pars tuberalis, it was necessary to define their cellular origin and thereby establish their status as representative thyrotrope cells for future molecular studies. In this study, we demonstrate that the T␣T1 cells express thyroid hormone receptors (␤1 and ␤2) and their heterodimeric partner, retinoid X receptor-␥. Treatment with T 3 causes a dose-and time-dependent decrease in the expression of the TSH ␤-subunit messenger RNA. In contrast to previous reports in rat pituitary cultures, T 3 does not alter TSH ␤-subunit messenger RNA stability in the T␣T1 cells. Based on these data and the presence of thyrotrope-specific isoforms of the transcription factor Pit-1, we conclude that the T␣T1 cells represent differentiated thyrotropes of the pars distalis and will be a useful model system for future analysis of the cis-and trans-acting factors necessary for thyrotrope-specific and thyroid hormone-regulated TSH gene expression. (Endocrinology 139: 4476 -4482, 1998) T SH OCCUPIES a centralized position in the hypothalamo-pituitary-thyroid axis and is responsible for maintaining appropriate thyroid hormone levels in the circulation. It indirectly plays a crucial role in maintaining vital metabolic functions and is a necessary component in clinical treatment regimens for diseases such as thyroid cancer and thyroid dysfunction. It is therefore important to delineate the underlying mechanisms that control expression of TSH in the thyrotrope cells of the anterior pituitary.TSH is a member of the glycoprotein hormone family and consists of two subunits, ␣ and ␤, that are encoded by distinct genes on different chromosomes (1). The ␣-subunit is shared by all members of the glycoprotein hormone family, including LH, FSH, and CG, in addition to TSH. The ␣-subunit gene is, therefore, expressed in three discrete cell types: the thyrotrope and gonadotrope cells of the anterior pituitary and the trophoblast cells of the placenta. In contrast, expression of the ␤-subunit of TSH is restricted to the thyrotrope cells. The cell type specificity exhibited by the ␤-subunit of TSH as well as the ␤-subunits of the ...

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Light and Electron Microscopic Immunocytochemistry of TSH-like Cells Occurring in the Pars tuberalis of the Adult Male Rat Pituitary.

Cited by 25 publications

References 24 publications

Glutamine and glutamic acid enhance thyroid-stimulating hormone β subunit mRNA expression in the rat pars tuberalis

Glutamine and glutamic acid enhance thyroid-stimulating hormone β subunit mRNA expression in the rat pars tuberalis

Expression of Tuberalin II, α-Subunit of Glycoprotein Hormones and β-Thyrotropin Hormone in the Pars Tuberalis of the Rat: Immunocytochemical Evidence for Pars Tuberalis-Specific Cell Types

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