Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

Magnan, E.; Mazzocchi, L; Cataldi, Mauro; Guillaume, Viviane; Dutour, A.; Dadoun, F.; Bouc, Yves Le; Sauze, Nicole; Renard, M; Conte-Devolx, B; Oliver, Charles

doi:10.1677/joe.0.1440083

Cited by 29 publications

(23 citation statements)

References 28 publications

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“…It is unclear as to why there is a small positive effect on basal GH secretion, yet a negative effect on GHRH-stimulated secretion, but the data are similar in the sheep (present study) and the pig [10]. Active immunization with GHRH antibodies markedly reduces, but does not abolish GH secretion [22], suggesting that a basal secretion of this hormone can occur in the absence of GHRH and is therefore a physiologically relevant component of the total level of GH that is measured in plasma.…”

Section: Discussionmentioning

confidence: 70%

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Roh

Clarke

et al. 1998

Neuroendocrinology

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We have studied the direct effect of leptin on the secretion of GH from the anterior pituitary gland of the sheep. Using primary cultures of ovine pituitary cells, leptin (10^–9–10^–7 M) treatment for 30 min did not affect basal or GHRH (10^–7 M)-stimulated GH secretion. Following treatment for 24 h, a dose of 10^–7 M leptin stimulated basal GH secretion. In contrast, doses of 10^–7 and 10^–8 M leptin inhibited GHRH-stimulated GH secretion after 24 h of treatment. These results suggest that leptin can have long-term effects on the somatotropes, but no acute effect. Furthermore, leptin appears to have opposite effects on basal and GHRH-stimulated GH secretion.

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Section: Discussionmentioning

confidence: 70%

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Roh

Clarke

et al. 1998

Neuroendocrinology

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“…However, some observations in the sheep, where a single administration of neostigmine, an Ach-E inhibitor, stimulated GHRH release into hypophysial portal blood without changes in SS levels (Magnan et al 1993(Magnan et al , 1995, challenge the view of a reciprocal and univocal relationship between SS function and the hypothalamic cholinergic system.…”

Section: Discussionmentioning

confidence: 99%

Growth hormone responses to growth hormone-releasing hormone and hexarelin in fed and fasted dogs: effect of somatostatin infusion or pretreatment with pirenzepine

Rigamonti¹,

Marazzi²,

Cella³

et al. 1998

Journal of Endocrinology

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Using unanesthetized young male and female beagle dogs, before and after a 2-day fast, we studied the effect of an i.v. infusion of 0·9% saline (5 ml/h), somatostatin (SS, 4 or 8 µg/kg/h) or pretreatment with pirenzepine (PZ, 0·6 mg/kg i.v.), a muscarinic cholinergic antagonist which allegedly releases SS, on the GH release evoked by acute administration of GHRH (2 µg/kg i.v.), hexarelin (HEXA), a member of the GH-releasing peptide family (250 µg/kg i.v.) or GHRH plus HEXA.In fasted dogs, GHRH delivered during saline infusion induced a clear-cut rise in plasma GH levels, significantly higher than that which it induced in fed dogs. In contrast, HEXA, although very effective in causing the release of GH, only slightly increased GH secretion in fasted dogs over that which it induced in fed dogs. Co-administration of GHRH plus HEXA into fed dogs induced a synergic GH response that further increased with fasting.The action of GHRH in fed dogs was abolished by the lower dose of SS, whereas SS at either dose was ineffective in suppressing the GH-releasing effect during fasting. Infusion of the lower dose of SS failed to counter the action of HEXA, either before or during fasting, whilst the higher SS dose partially reduced it in both conditions.In contrast to SS, PZ reduced the GH-releasing effect of GHRH and HEXA, both in the fed state and, though to a lesser extent, during fasting. Pirenzepine only slightly reduced the robust GH rise elicited by GHRH plus HEXA in fed dogs. The suppressive effect of PZ on the GH response to combined administration of the peptides was lowest in fasted dogs.These data show that: (1) fasting augmented the GH response to GHRH and (to a lesser degree) to HEXA; (2) SS inhibited the GH response to GHRH in the fed state, but not in the fasted state; (3) only the higher dose of SS partially reduced the GH stimulation by HEXA in either the fed or the fasted state; (4) PZ lowered the GH response to GHRH and to HEXA in both the fed and (to a lesser degree) the fasted state; (5) PZ did not modify the GH release due to the combined administration of GHRH and HEXA.It is suggested that: (1) during fasting the greatly enhanced GH response to GHRH alone or GHRH plus HEXA probably reflects an augmented GHRH secretion; (2) somatotrope refractoriness to SS may contribute to the enhanced GH secretion in states of calorie deprivation; (3) in contrast to a general belief, muscarinic cholinergic antagonists, e.g. PZ, do not act exclusively via release of SS, but probably also through inhibition of GHRH function.

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“…Indeed, pulsatile spontaneous GH release (6, 7) as well as neostigmine- (8), clonidine- (9), and tianeptine- (10) induced GH secretion were associated with an increased release of GHRH into HPB without significant changes in SRIH levels. In this species, active immunization against SRIH did not affect GH secretion while a striking reduction in plasma GH concentrations was observed in the group of anti-GHRH animals (11). GH response to an acute GHRH stimulation was even lower in the anti-SRIH group than in the control group, suggesting that SRIH could be involved in GH regulation through the prevention of GH stores depletion and/or GHRH receptor desensitization (12,13).…”

Section: Introductionmentioning

confidence: 91%

Species differences between male rat and ram pituitary somatostatin receptors involved in the inhibition of growth hormone secretion

Briard

Dutour

Epelbaum

et al. 1997

European Journal of Endocrinology

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The sheep is a valuable model in which to study GH neuroregulation as its pattern of GH secretion is very close to that in humans. Furthermore, important differences in somatostatin (SRIH) action between rats and sheep have been found previously. Our goal was to compare in male rat and ram pituitaries the binding characteristics of somatostatin receptors and the effect of SRIH and 17 analogues on GH release. Using radioautography, SRIH binding was seen to be evenly distributed over the anterior pituitary of both species. In the binding assay, binding sites were three times more concentrated in rats than in sheep. Important interspecies differences in the action of SRIH and its analogues were found: they inhibited GH at lower concentrations in rats than in sheep. Seven peptides displayed greater inhibitory ability in sheep than in rats while three were more potent in rats. Agonistic potencies to inhibit GH release in rats were correlated with somatostatin receptors subtype 2 (sst2) affinities. Our data confirm and extend the quantitative differences between rat and sheep in SRIH inhibitory action on GH secretion and confirm that ligand-binding properties of a given receptor subtype cannot be extrapolated across species. European Journal of Endocrinology 137 545-555

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Effect of actively immunizing sheep against growth hormone-releasing hormone or somatostatin on spontaneous pulsatile and neostigmine-induced growth hormone secretion

Cited by 29 publications

References 28 publications

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

The in vitro Effect of Leptin onBasal and Growth Hormone-Releasing Hormone-StimulatedGrowth Hormone Secretion from theOvine Pituitary Gland

Growth hormone responses to growth hormone-releasing hormone and hexarelin in fed and fasted dogs: effect of somatostatin infusion or pretreatment with pirenzepine

Species differences between male rat and ram pituitary somatostatin receptors involved in the inhibition of growth hormone secretion

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