Enhancement by Prolactin of the GnRH-Induced Release of LH from Dispersed Anterior Pituitary Cells of the Bullfrog (Rana catesbeiana)

Oguchi, Atsuko; Tanaka, Shigeyasu; Aida, T; Yamamoto, Kazutoshi; Kikuyama, Sakaé

doi:10.1006/gcen.1997.6904

Cited by 17 publications

(8 citation statements)

References 48 publications

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“…Ghrelin activity was observed in 16 sequential fractions (numbers 18 -32). A portion of the active peak, P1 (fraction [25][26][27][28][29], contained the highest activity. These pooled fractions were subjected to immunoaffinity chromatography using an IgG antiserum raised against rat ghrelin (1)(2)(3)(4)(5)(6)(7)(8)(9)(10)(11).…”

Section: Resultsmentioning

confidence: 99%

“…The activity of each fraction was determined by subjecting a 50-mg tissue equivalent to FLIPR analysis. Active peak, P1 (fraction [25][26][27][28][29], was diluted in an equal volume of 0.1% TFA. The lyophilized sample was subsequently dissolved in 500 l of 100 mM phosphate buffer (pH 7.4).…”

Section: Methodsmentioning

confidence: 99%

“…The resulting media (150 l) were collected in V-bottom 96-well microplates (Iwaki, Tokyo, Japan) following centrifugation at 100 ϫ g for 5 min to remove cell debris. The collected medium (100 l) was stored at Ϫ20°C until use in a homologous radioimmunoassay for GH (22), PRL (23), FSH (24), and LH (25).…”

Section: Methodsmentioning

confidence: 99%

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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: Resultsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

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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

View full text Add to dashboard Cite

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“…These observations were confirmed by Siperstein and Miller (315) and Yoshimura and Nogami (316, 317). The lactotroph–gonadotroph associations were also reported in horse (302, 318), sheep (301), chicken (319) and frog pituitary (304). Associations between lactotrophs and gonadotrophs reconstitute in monolayer cultures of densely plated cells (320) and in reaggregate pituitary cell cultures (321), indicating that the affinity between cell types is locally regulated.…”

Section: Close Association Between Cup-shaped Lactotrophs and Gonadotmentioning

confidence: 82%

“…PRL has been shown not to tonically inhibit GnRH-stimulated LH release in rat monolayer cell culture (303). However, either intravenous administration of PRL or raising plasma PRL levels by immobilisation stress, reduced the LH response to GnRH pulses and GnRH-stimulated increase in GnRH-R density, whereas addition of antiserum against PRL lowered the responsiveness of LH cells to GnRH, consistent with a paracrine inhibitory tone of PRL on LH secretion (304). In sheep, PRL on its own was found to inhibit (305) or not affect (306) GnRH-induced LH release in culture but, in the presence of a dopamine agonist, it completely blocked it, at least when cells are taken in the nonbreeding season (306).…”

Section: Gonadotrophs As Paracrine Targetsmentioning

confidence: 99%

Endogenous Cannabinoids: Structure and Metabolism

Bisogno

2008

J Neuroendocrinology

144

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D9 -Tetrahydrocannabinol (THC), the main psychoactive compound extracted from Cannabis sativa, is the most representative component of the mixture of therapeutic substances that are communally referred to as cannabinoids (1). It acts as an agonist at specific G-protein-coupled receptors, cannabinoid receptor subtypes CB 1 and CB 2 (2). The discovery of cannabinoid receptors has driven the investigation of the existence of their natural ligands and, soon after, endocannabinoids were identified. N-arachidonoyl-ethanolamine (AEA, anandamide) and 2-arachidonoyl glycerol (2-AG) are the two most studied endocannabinoids. They are biosynthesised 'on demand' by cleavage of their membrane lipid precursors N-arachidonoyl-phosphatidylethanolamine (N-ArPE) and sn-1-acyl-2-arachidonoylglycerols (DAGs) respectively, and then inactivated by intracellular hydrolysing enzymes. Cannabinoid receptors, endocannabinoids and enzymes that biosynthesise [N-acyl-phosphatidylethanolamine-selective phospholipase D (NAPE-PLD) and diacylglycerol lipase (DAGL)] and degrade [fatty acid amide hydrolase (FAAH) and the monoacylglycerol lipases (MAGL)] AEA and 2-AG, respectively, are key components in the endocannabinoid system (3). Despite a large number of excellent studies having contributed to the current understanding of the endocannabinoid regulation and function, further efforts are necessary to fully comprehend this signalling system. Here, a review on the current knowledge on structure and metabolism of the best studied endogenous cannabinoids is presented. In particular, this review concentrates on the mechanisms responsible for the biosynthesis and inactivation of the endocannabinoids, as well as on the several inhibitors of their metabolism identified to date. Endocannabinoids and related N-acyl-ethanolaminesEndocannabinoids are defined as endogenous compounds capable of binding to and functionally activating cannabinoid receptors. At least five endocannabinoids have been identified to date (Fig. 1). Anandamide, the amide between arachidonic acid and ethanolamine, was the first endogenous ligand to be reported at the end of 1992 (4) and additional polyunsaturated ethanolamines that bind to cannabinoid receptors, homolinolenylethanolamide and docosatetraenylethanolamide, have been isolated in the brain. Other endocannabinoids, all derived from arachidonic acid, were identified. The identification of 2-AG, the ester of arachidonic acid with glycerol, isolated from canine gut and brain has also been reported (5, 6). Subsequently, the first endocannabinoid characterised by ether bond, 2-arachidonyl glyceryl ether or noladin ether, was isolated from porcine brain (7) and N-arachidonoyldopamine (NADA), a selective CB 1 agonist and a potent agonist of vanilloid receptors, was discovered (8, 9). O-arachidonoylethanolamine, the ester derivative of ethanolamine with arachidonic acid, with the same molecular weight as anandamide but with opposite orientation of the polar ethanolamine moiety, was named virodhamine from the Sanskrit word virodha, ...

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Central regulation of reproduction in amphibians

Hasunuma

2023

J Exp Zool Pt A

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This review article includes a literature review of synteny analysis of the amphibian gonadotropin‐releasing hormone (GnRH) genes, the distribution of GnRH 1 and GnRH2 neurons in the central nervous system of amphibians, the function and regulation of hypophysiotropic GnRH1, and the function of GnRH1 in amphibian reproductive behaviors. It is generally accepted that GnRH is the key regulator of the hypothalamic–pituitary–gonadal axis. Three independent GnRH genes, GnRH1, GnRH2, and GnRH3, have been identified in vertebrates. Previous genome synteny analyses suggest that there are likely just two genes, gnrh1 and gnrh2, in amphibians. In three groups of amphibians: Anura, Urodela, and Gymnophiona, the distributions of GnRH1 and GnRH2 neurons in the central nervous system have also been previously reported. Moreover, these neuronal networks were determined to be structurally independent in all species examined. The somata of GnRH1 neurons are located in the terminal nerve, medial septum (MS), and preoptic area (POA), and some GnRH1 neurons in the MS and POA project into the median eminence. In contrast, the somata of GnRH2 neurons are located in the midbrain tegmentum. In amphibians, GnRH1 neurons originate from the embryonic olfactory placode, while GnRH2 neurons originate from the midbrain. The characterization and feedback regulation mechanisms of hypophysiotropic GnRH1 neurons in amphibians, the involvement of GnRH1 in amphibian reproductive behavior, and its possible mechanism of action should be elucidated in future.

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Enhancement by Prolactin of the GnRH-Induced Release of LH from Dispersed Anterior Pituitary Cells of the Bullfrog (Rana catesbeiana)

Cited by 17 publications

References 48 publications

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

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

Endogenous Cannabinoids: Structure and Metabolism

Central regulation of reproduction in amphibians

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