Gonadotrophs but not somatotrophs carry gonadotrophin-releasing hormone receptors: receptor localisation, intracellular calcium, and gonadotrophin and GH release

Bosma, Peter T.; Kolk, Sharon M.; Rebers, F.E.M.; Lescroart, Olivier; Roelants, Ivo; Willems, Peter H.G.M.; Schulz, Ralph

doi:10.1677/joe.0.1520437

Cited by 40 publications

(23 citation statements)

References 51 publications

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“…GHRH does not show any effect on GH secretion in the eel (Montero et al 1998, Rousseau et al 1999. GnRH stimulates the release of GH in goldfish, common carp and tilapia, but no effect is seen in the trout (Blaise et al 1995), catfish (Bosma et al 1997) or eel (Rousseau et al 1999). TRH induces the release of GH in the goldfish and common carp, but not in the tilapia (Melamed et al 1995) or eel (Rousseau et al 1999).…”

Section: Introductionmentioning

confidence: 80%

Amidated fish ghrelin: purification, cDNA cloning in the Japanese eel and its biological activity

Kaiya¹,

Kojima²,

Hosoda³

et al. 2003

Journal of Endocrinology

136

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We purified ghrelin from stomach extracts of a teleost fish, the Japanese eel (Anguilla japonica) and found that it contained an amide structure at the C-terminal end. Two molecular forms of ghrelin with 21 amino acids were identified by cDNA and mass spectrometric analyses: eel ghrelin-21, GSS(O-n-octanoyl)FLSPSQRPQGKDKKPP RV-amide and eel ghrelin-21-C10, GSS(O-n-decanoyl) FLSPSQRPQGKDKKPPRV-amide. Northern blot and RT-PCR analyses revealed high gene expression in the stomach. Low levels of expression were found only in the brain, intestines, kidney and head kidney by RT-PCR analysis. Eel ghrelin-21 increased plasma growth hormone (GH) concentrations in rats after intravenous injection; the potency was similar to that of rat ghrelin. We also examined the effect of eel ghrelin on the secretion of GH and prolactin (PRL) from organ-cultured tilapia pituitary. Eel ghrelin-21 at a dose of 0·1 nM stimulated the release of GH and PRL, indicating that ghrelin acts directly on the pituitary. The present study revealed that ghrelin is present in fish stomach and has the ability to stimulate the secretion of GH from fish pituitary. A novel regulatory pathway of GH secretion by gastric ghrelin seems to be conserved from fish to human.

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Section: Introductionmentioning

confidence: 80%

Amidated fish ghrelin: purification, cDNA cloning in the Japanese eel and its biological activity

Kaiya¹,

Kojima²,

Hosoda³

et al. 2003

Journal of Endocrinology

136

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“…GnRH stimulated GH release in the goldfish [14, 67]and tilapia [9], but not in the catfish [10, 16]or European eel [13]. In our studies on juvenile turbot, we have tested the three forms of GnRH (sbGnRH, sGnRH, cGnRH-II) expressed in recent teleosts (percomorphs) but none of them were active.…”

Section: Discussionmentioning

confidence: 99%

“…GHRH has been reported to stimulate GH release in goldfish [6], rainbow trout [7, 8], tilapia [9]and catfish [10]but had a very low and non-dose-dependent effect in the salmon [11], and no effect in the European eel [12, 13]. Gonadotropin-releasing hormone (GnRH) strongly stimulated GH release in goldfish [14], carp [15], tilapia [9], but not in trout [8], catfish [16], or European eel [13]. TRH activated GH release in goldfish [17], carp [18, 19], but not tilapia [9], or European eel [13].…”

Section: Introductionmentioning

confidence: 99%

Pituitary Growth Hormone Secretion in the Turbot, a Phylogenetically Recent Teleost, Is Regulated by a Species-Specific Pattern of Neuropeptides

et al. 2001

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In mammals, growth hormone (GH) is under a dual hypothalamic control exerted by growth hormone-releasing hormone (GHRH) and somatostatin (SRIH). We investigated GH release in a pleuronectiform teleost, the turbot (Psetta maxima), using a serum-free primary culture of dispersed pituitary cells. Cells released GH for up to 12 days in culture, indicating that turbot somatotropes do not require releasing hormone for their regulation. SRIH dose-dependently inhibited GH release up to a maximal inhibitory effect of 95%. None of the potential stimulators tested induced any change in basal GH release. Also, neither forskolin, an activator of adenylate cyclase, nor phorbol ester (TPA), an activator of protein kinase C, were able to modify GH release, suggesting that spontaneous basal release already represents the maximal secretory capacity of turbot somatotropes. In contrast, forskolin and TPA were able to increase GH release in the presence of SRIH. In this condition (coincubation with SRIH), pituitary adenylate cyclase-activating polypeptide (PACAP) stimulated GH release, whereas none of the other neuropeptides tested (GHRHs; sea bream or salmon or chicken II GnRHs; TRH; CRH) had any significant effect. These data indicate that inhibitory control by SRIH may be the basic control of GH production in teleosts and lower vertebrates, while PACAP may represent the ancestral growth hormone-releasing factor in teleosts, a role taken over in higher vertebrates by GHRH.

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“…We have previously shown that gonadotrophs were the only cell type in an African catfish pituitary cell suspension displaying GnRH binding activity [14]. Furthermore, we demonstrated that the effects of both cfGnRH and cGnRH-II on the cytosolic free calcium concentration ([Ca 2ϩ ] i ) in gonadotrophs in vitro are correlated with their potency to induce LH secretion, both in vitro and in vivo [12,14].…”

Section: Introductionmentioning

confidence: 88%

Inhibitory and Stimulatory Interactions Between Endogenous Gonadotropin-Releasing Hormones in the African Catfish (Clarias gariepinus)1

Bosma

Rebers

Dijk

et al. 2000

Biology of Reproduction

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In the brain of all vertebrate classes, chicken (c) GnRH-II ([His(5), Trp(7),Tyr(8)]GnRH, cGnRH-II) is expressed in the mesencephalon. In addition, at least one other form of GnRH is expressed in the preoptical area/hypothalamus. In the human pituitary stalk and the mouse median eminence, cGnRH-II is present together with mammalian GnRH. Similarly, in the pituitary of several teleost fish (e.g., goldfish and eel, but not salmon or trout), a teleost GnRH is found together with cGnRH-II. These GnRHs are not colocalized in the same cells. Hence, these GnRH peptides may differentially regulate gonadotropin secretion and, in addition, may exert their effects simultaneously. The current study therefore investigated the effects of combinations of the two forms of GnRH present in the African catfish (Clarias gariepinus) pituitary-cGnRH-II and catfish GnRH ([His(5),Asn(8)]GnRH, cfGnRH)-on the cytosolic free calcium concentration ([Ca(2+)](i)) in single, Fura-2-loaded catfish gonadotrophs, as well as their effects on both in vitro and in vivo LH secretion. Both inhibitory and stimulatory effects of combinations of cfGnRH and cGnRH-II on [Ca(2+)](i) were observed, which were mirrored by their effects on both in vitro and in vivo LH secretion. The following pattern became apparent. The effect of intermediate or maximal effective cfGnRH doses was inhibited by the simultaneous presence of subthreshold or borderline effective cGnRH-II doses. Conversely, subthreshold or borderline effective concentrations of cfGnRH enhanced the effects of intermediate and maximal concentrations of cGnRH-II. In addition, combinations of cfGnRH and cGnRH-II concentrations that were equally active when tested separately showed an additive effect. The observed interactions between the two GnRHs may be of particular physiological relevance in the control of seasonal LH levels in the African catfish, as well as in other teleost species. Moreover, the occurrence of mutual inhibitory and stimulatory interactions between endogenous GnRHs may be a widespread aspect of GnRH action in vertebrates.

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Gonadotrophs but not somatotrophs carry gonadotrophin-releasing hormone receptors: receptor localisation, intracellular calcium, and gonadotrophin and GH release

Cited by 40 publications

References 51 publications

Amidated fish ghrelin: purification, cDNA cloning in the Japanese eel and its biological activity

Amidated fish ghrelin: purification, cDNA cloning in the Japanese eel and its biological activity

Pituitary Growth Hormone Secretion in the Turbot, a Phylogenetically Recent Teleost, Is Regulated by a Species-Specific Pattern of Neuropeptides

Inhibitory and Stimulatory Interactions Between Endogenous Gonadotropin-Releasing Hormones in the African Catfish (Clarias gariepinus)1

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