Distribution of Endothelin 3-Like Immunoreactivity in Gonadotrophs of the Bullfrog (Rana catesbeiana) Pituitary

Suzuki, Hirohumi; Yamamoto, Toshiharu; Kikuyama, Sakaé; Uemura, Hirotsugu

doi:10.1006/gcen.1997.6899

Cited by 19 publications

(10 citation statements)

References 49 publications

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“…These results indicate that the regulatory mechanism governing GH secretion by GHRH exists in the frog. In addition, thyrotropinreleasing hormone (27), proopiomelanocortin-derived peptides (27), pituitary adenylate cyclase-activating polypeptide (34), and endothelin (35) are involved in GH release in the frog. These facts indicate that the stimulation of GH secretion in 6.…”

Section: Rna B Rt-pcr Analysis Poly(a)mentioning

confidence: 99%

Bullfrog Ghrelin Is Modified by n-Octanoic Acid at Its Third Threonine Residue

Kaiya¹,

Kojima²,

Hosoda³

et al. 2001

Journal of Biological Chemistry

155

101

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We have identified the amphibian ghrelin from the stomach of the bullfrog. We also examined growth hormone (GH)-releasing activity of this novel peptide in both the rat and bullfrog. The three forms of ghrelin identified, each comprised of 27 or 28 amino acids, possessed 29% sequence identity to the mammalian ghrelins. A unique threonine at amino acid position 3 (Thr 3 ) in bullfrog ghrelin differs from the serine present in the mammalian ghrelins; this Thr 3 is acylated by either n-octanoic or n-decanoic acid. The frog ghrelin-28 has a complete structure of GLT (O-n-octanoyl)FLSPAD-MQKIAERQSQNKLRHGNM; the structure of frog ghrelin-27 was determined to be GLT(O-n-octanoyl)FLSPAD-MQKIAERQSQNKLRHGN; frog ghelin-27-C10 possessed a structure of GLT(O-n-decanoyl)FLSPADMQKIAER-QSQNKLRHGN. Northern blot analysis demonstrated that ghrelin mRNA is predominantly expressed in the stomach. Low levels of gene expression were observed in the heart, lung, small intestine, gall bladder, pancreas, and testes, as revealed by reverse transcription polymerase chain reaction analysis. Bullfrog ghrelin stimulated the secretion of both GH and prolactin in dispersed bullfrog pituitary cells with potency 2-3 orders of magnitude greater than that of rat ghrelin. Bullfrog ghrelin, however, was only minimally effective in elevating plasma GH levels following intravenous injection into rats. These results indicate that although the regulatory mechanism of ghrelin to induce GH secretion is evolutionary conserved, the structural changes in the different ghrelins result in species-specific receptor binding. Growth hormone (GH)1 secretion from the pituitary gland is regulated by hypothalamic hormones; growth hormone-releasing hormone (GHRH) stimulates GH secretion, whereas somatostatin is inhibitory (1). Derivatives of Met-enkephalin stimulate GH release (2), the first demonstration that small synthetic peptides and nonpeptide molecules, dubbed growth hormone secretagogues (GHSs), can mediate GH release through a receptor distinct from that of GHRH (3-5). The G-protein-coupled GHS receptor (GHS-R) was subsequently identified in swine, rat, and human (6, 7), suggesting that one or more unknown ligands for this receptor are endogenously present.We recently discovered an endogenous ligand for GHS-R from the rat stomach, using an intracellular calcium influx assay in stable cell lines expressing rat GHS-R (8). This novel molecule, a 28-amino acid peptide named ghrelin (from "ghre," the Proto-Indo-European root of "grow"), possesses a unique serine residue at the third N-terminal position (Ser 3 ) that is n-octanoylated (8, 9). Acylation of Ser 3 is essential for ghrelin bioactivity. cDNA analysis revealed that the rat ghrelin sequence follows the 23-residue signal sequence within the 117-residue prepro-ghrelin. Ghrelin stimulates GH secretion both in vivo and in vitro. Accumulating evidence in mammals suggests that, in addition to regulating GH release, ghrelin also influences feeding behavior (10, 11), gastrointestinal function (12, 13), and ener...

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Section: Rna B Rt-pcr Analysis Poly(a)mentioning

confidence: 99%

Bullfrog Ghrelin Is Modified by n-Octanoic Acid at Its Third Threonine Residue

Kaiya¹,

Kojima²,

Hosoda³

et al. 2001

Journal of Biological Chemistry

155

101

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“…Endothelins have been reported to induce thyroid-stimulating hormone (TSH), lutenizing hormone (LH), follicle-stimulating hormone (FSH) and adrenocorticotropic hormone (ACTH), but to inhibit prolactin release in vitro (Samson et al 1990; Kanyicska et al 1991;Samson 1992;Kanyicska and Freeman 1993;Calogero et al 1994;Zheng et al 1995;Stojilkovic and Catt 1996;Kanyicska et al 1998). Moreover, ET immunoreactivity has been detected not only in the neural lobe (Nakamura et al 1993;Uemura et al 1994), but in the gonadotrophs (Naruse et al 1992;Suzuki et al 1997). Endothelins in the pituitary are considered as modulators of secretory responses, or autocrine and/or paracrine hormones (Kanyicska et al 1998).…”

Section: Introductionmentioning

confidence: 97%

Localization of endothelin A receptors in the rat pituitary TSH cells: light- and electron-microscopic immunohistochemical studies

Furuya

Hiroe

Ozaki

et al. 2000

Cell and Tissue Research

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Endothelins modulate hormonal secretion in the pituitary gland. Intense signaling of endothelin A receptors (ET(A)R) has been detected by in situ hybridization, binding assay and receptor autoradiography. We used light- and electron-microscopic immunohistochemistry of ET(A)R with polyclonal antibody against a synthetic peptide corresponding to the carboxyl terminus (403-427) of human ET(A)R. Immunoreactivity was observed in 6-8% of anterior pituitary cells, which were rather large polygonal or stellate cells. These cells were often clustered. Double-staining immunofluorescence showed that the ET(A)R-positive cells immunoreacted with antibody against the beta-subunit of thyroid-stimulating hormone (TSH), but not adrenocorticotropic hormone (ACTH) or lutenizing hormone beta (LHbeta). Pre- and postembedding electron-microscopic immunohistochemistry showed that ET(A)R-positive cells had vacuolated or parallel-lined rough endoplasmic reticulum (rER) and numerous round granules in their periphery and the elongated processes. By pre-embedding immunohistochemistry, diaminobenzidine tetrahydrochloride (DAB) products were shown to be mostly located around the granules and occasionally underneath the plasma membrane. By postembedding immunohistochemistry, granules in the ET(A)R-positive cells were 90-150 nm in diameter, and colloidal gold particles due to ET(A)R were associated with about 10% of these granules. These results indicate that ET(A) receptors are associated mostly with the secretory granules of TSH cells.

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“…Immunohistochemistry was mainly performed according to our routine method (Suzuki et al, 1997). Briefly, the sections were washed overnight in 0.1 M PB (pH 7.4) containing 0.9% saline (PBS), and incubated with rabbit anti-human orexin-A antiserum (Peptide Institute, Osaka, Japan) diluted 1:500 to 1:2000 in PBS containing 1% bovine serum albumin (BSA) and 0.3% Triton X-100 (PBS-BSAT) for 24 h at 4 8C.…”

Section: Immunohistochemistrymentioning

confidence: 99%