Evidence for Gene Transcription of Adenohypophyseal Hormones in the Ovine Pars tuberalis

Böckers, Tobias M.; Bockmann, Jürgen; Fauteck, Jan-Dirk; Wittkowski, W.; Sabel, Bernhard A.; Kreutz, Michael R.

doi:10.1159/000126931

Cited by 19 publications

(22 citation statements)

References 31 publications

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“…Furthermore, it has been shown that in the hamster PT, the expression of β-TSH is regulated by the photoperiod [15,16]. In other mammals, such as sheep, mRNAs encoding for the 3 PD-glycoprotein hormones have been demonstrated in the PT, although only GSU and β-LH have been revealed by immunocytochemistry [17,18,19]. …”

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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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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“…The PT is mainly composed of secretory active PTspecific cells (11,12). PT-specific cells represent a distinct hypophyseal cell type that transcribes TSH␣ and -␤ in a considerable amount in all species investigated to date, but does not resemble thyrotropes of the pars distalis (PD) (13).…”

Section: Introductionmentioning

confidence: 99%

Thyrotropin Expression in Hypophyseal Pars Tuberalis-Specific Cells is 3,5,3′-Triiodothyronine, Thyrotropin-Releasing Hormone, and Pit-1 Independent*

et al. 1997

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The expression of TSH subunit genes (TSH␣ and -␤) in pituitary thyrotropes is primarily regulated via circulating thyroid hormone levels (T 3 ) and the hypothalamic TRH. Hypophyseal pars tuberalis (PT)-specific cells also express both hormonal subunits of TSH, but do not resemble thyrotropes of the pars distalis (PD) with respect to their distinct morphology, secretion, and direct modulation of TSH expression by photoperiodic inputs and melatonin. To investigate whether this distinct regulation of TSH is related to a different molecular structure or different signaling cascades, we analyzed PT-specific TSH and its transcriptional regulation in ovine PT-specific cells. After construction of PT-and PD-specific complementary DNA (cDNA) libraries, the cloning and sequencing of several TSH␣ and -␤ subunit clones revealed identical sizes and sequences for the translated and untranslated regions in both hypophyseal compartments. Transcription start site analysis also displayed three identical start sites for the transcription of TSH␤ in PT and PD. After cloning of the ovine TRH receptor cDNA and a partial T 3 receptor cDNA, in situ hybridization, Northern blot analysis, and PCR experiments showed that TRH and T 3 receptors are not expressed in specific cells of the PT. The transcription factor Pit-1 that is involved in TSH expression of thyrotropes could only be detected in the PD.In additional experiments rats were treated with T 4 or TRH, and subsequent in situ hybridization studies showed that TSH␤ messenger RNA (mRNA) formation was not altered in the PT. In the PD, however, TSH␤ mRNA was significantly reduced in the T 4 -treated group, but was enhanced in the TRH-treated group. We conclude that PT-specific cells of the pituitary are characterized by the transcription of TSH subunits that are identical to TSH expressed in thyrotropes of the PD. The absence of TRH, T 3 receptor mRNA, and Pit-1, respectively, as well as the different reactions compared to PD thyrotropes in in vivo experiments lead to the conclusion that the expression of TSH in PT-specific cells of the pituitary is not regulated via the classical thyrotrope receptors and their intracellular pathways, but through a novel, photoperiod-dependent mechanism. (Endocrinology 138: 1019 -1028, 1997) T HE HYPOPHYSEAL glycoprotein hormone, TSH, consists of two noncovalently bound subunits, ␣ and ␤, which are encoded by separate genes on different chromosomes (1). The ␣-subunit is common to the other members of the glycoprotein hormone family, pituitary LH and FSH and placental CG, whereas the unique ␤-subunit determines the specificity of the hormonal dimer (2). The expression and secretion of TSH␣ and -␤ subunits in pituitary thyrotropes are closely regulated by hypothalamic factors released from the median eminence into the hypophyseal blood flow, in particular TRH, and a feedback control by thyroid hormones (e.g. T 3 ) (3, 4). T 3 acts as a suppressor of TSH transcription after attachment to a nuclear T 3 receptor (TR␤) that binds as a T 3 -receptor c...

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“…However, expression of further necessary genes does not follow (Lanctot et al, 1999). These cells do not react with a specific antibody against the ␤-subunit of LH (Böckers et al, 1996;Stoeckel et al, 1994). The folliculostellate cells of the PT differ from those described in the PD (Kameda, 1996a(Kameda, , 1996b.…”

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confidence: 88%

“…The PT is a bi-or multilayered region formed by specific secretory cells (the so-called PT-specific cells), folliculostellate cells, and migratory cells coming from the PD (Oota and Kurosomi, 1966;Cameron and Foster, 1972;Stoeckel and Porte, 1984). The diameter of the secretory granules differs according to the species (Dellman et al, 1974) The presence in the PT caudal zone of hormones produced in the PD, particularly LH, FSH, and TSH, has been demonstrated in some species by immunocytochemical techniques (Baker and Yu, 1975;Girod et al, 1980;Asa et al, 1983;Gross, 1984;Böckers et al, 1996). These endocrine products are considered to be synthesized by migratory cells coming from the PD.…”

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confidence: 99%

Ultrastructural and immunocytochemical studies of the viscacha (Lagostomus maximus maximus) pituitary pars tuberalis

et al. 2005

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The hypophyseal pars tuberalis (PT) has been the focus of numerous studies attempting to understand its physiological role in the reproductive regulation and modulation by the neuroendocrine system. Ultrastructural studies of the PT in a number of species have shown that it consists of a well-developed hypophyseal area with important secretory activity, demonstrated by the abundance of secretory granules in the cytoplasm and the marked blood irrigation. This article describes ultrastructural and immunocytochemical aspects of the PT in viscachas captured in their habitat. The cell types identified were PT-specific cells, agranulated cells, and Folliculostellate cells. PT-specific cells are divided into type I and II. Type I cells have cytoplasms with secretory granules of 150-500 nm diameter. The secretory granules of type II PT-specific cells are 65-200 nm in diameter. Both cellular types exhibit numerous nerve endings on the plasmatic membranes. Agranulated cells exhibit nuclei with lax chromatin, mitochondria, phagosomes, scarce Golgi complex, and rough endoplasmic reticulum. Folliculostellate cells exhibit an irregularly shaped and moderately condensed nucleus. All the described cellular types exhibit deposits of cytoplasmic glycogen. The immunocytochemical study revealed the presence of cells immunostained for LH-␤ and FSH-␤ in the PT caudal zone. ACTH was only detected in the zona tuberalis. No staining was observed with antiprolactin, anti-TSH-␤, and anti-GH sera. Folliculostellate cells exhibited staining with anti-S-100. The results demonstrate that the viscacha PT is a hypophyseal zone with specific cellular types, which exhibits evident secretory activity. The presence of nerve endings suggests neural control of the function of PT cells.

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Evidence for Gene Transcription of Adenohypophyseal Hormones in the Ovine Pars tuberalis

Cited by 19 publications

References 31 publications

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

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

Thyrotropin Expression in Hypophyseal Pars Tuberalis-Specific Cells is 3,5,3′-Triiodothyronine, Thyrotropin-Releasing Hormone, and Pit-1 Independent*

Ultrastructural and immunocytochemical studies of the viscacha (Lagostomus maximus maximus) pituitary pars tuberalis

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