Acute changes in growth hormone-releasing hormone secretion after injection of BIM 23014, a long acting somatostatin analog, in rams

Magnan, E.; Cataldi, Mauro; Guillaume, Viviane; Conte-Devolx, B.; Graziani, N; Figaroli, J C; Thomas, François; Chihara, Kazuo; Oliver, Charles

doi:10.1016/0024-3205(92)90610-2

Cited by 38 publications

(30 citation statements)

References 36 publications

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“…At the 6th week, the GH response to GHRH was attenuated, but was still comparable to that induced by GHRH at pretreatment. Similar, but not superimposable, results were obtained in our study by evaluating, albeit inferentially, hypothalamic GHRH neurones freed from the inhibitory influences of somatostatin (22)(23)(24). Following somatostatin infusion, the rebound increase in GH was enhanced at the 3rd week, but completely abolished at the 6th week.…”

Section: Discussionsupporting

confidence: 87%

“…The extent of the GH response at the termination of the somatostatin infusion was taken to reflect the endogenous GHRH function (22)(23)(24).…”

Section: Somatostatin Infusionmentioning

confidence: 99%

“…In this context, it is of note that we (22,23) and others (24) have proposed the use of the rebound GH release that follows withdrawal of an infusion of somatostatin as a useful tool with which to evaluate endogenous GHRH function.…”

Section: Introductionmentioning

confidence: 99%

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Six-week treatment with hexarelin in young dogs: evaluation of the GH responsiveness to acute hexarelin or GHRH administration, and of the orexigenic effect of hexarelin

Rigamonti

Cella

Marazzi

et al. 1999

European Journal of Endocrinology

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In this study we evaluated, in six young (5-7 year-old) beagle dogs, the effects of a 6-week administration of hexarelin (250 mg/kg s.c. twice daily) on the GH response to an acute challenge with hexarelin or GHRH (2 mg/kg i.v.), delivered before and after 3 and 6 weeks of treatment. The GH peak response to acute hexarelin or GHRH initially increased, with a maximum observed at the 3rd week, and then decreased to basal values (GHRH) or less (hexarelin) at the 6th week. These data would indicate that hexarelin initially primed the pituitary to acute administration of further hexarelin or of GHRH, followed by downregulation of the GH response to hexarelin and preservation of the response to GHRH. We then studied the rebound increase in GH secretion after withdrawal of an infusion of somatostatin (4 mg/kg per h for 1.5 h), a likely stimulus of endogenous GHRH function. The pattern obtained was similar to, though not superimposable upon, that ensuing after acute hexarelin or GHRH administration. Parallel evaluation of the acute orexigenic effect of hexarelin evinced a different timecourse of the behavioural response, namely an acute feeding response to hexarelin that was abolished at the 3rd week and returned to normal at the 6th week. The differing timing of the neuroendocrine or behavioural response to hexarelin would suggest the existence of different subtypes of central nervous system GH-releasing peptide receptors.

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Section: Discussionsupporting

confidence: 87%

“…The extent of the GH response at the termination of the somatostatin infusion was taken to reflect the endogenous GHRH function (22)(23)(24).…”

Section: Somatostatin Infusionmentioning

confidence: 99%

See 1 more Smart Citation

Six-week treatment with hexarelin in young dogs: evaluation of the GH responsiveness to acute hexarelin or GHRH administration, and of the orexigenic effect of hexarelin

Rigamonti

Cella

Marazzi

et al. 1999

European Journal of Endocrinology

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“…In the present study, intravenous injections of SRIF blunted xylazine-induced GH release in calves. This suggested that exogenous SRIF inhibited xylazine-induced GH release at the pituitary level, but since SRIF can inhibit release of GHRH [25,26], the increased GHRH release induced by xylazine might have been partially inhibited by SRIF in the present study.…”

Section: Discussionmentioning

confidence: 54%

Effects of Atipamezole, an .ALPHA.2-Adrenergic Antagonist, and Somatostatin on Xylazine-lnduced Growth Hormone Release in Calves.

et al. 1996

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Abstract. In order to clarify the mechanism of xylazine-induced GH release, we investigated the effects of atipamezole, a selective a2-adrenergic antagonist, and somatostatin (SRIF) on xylazine-stimulated GH release in calves. Xylazine injection (0.30 mg/kg BW, iv) induced a rapid increase in the GH concentration. When atipamezole was used in combination with xylazine, it blunted the increase in the plasma GH concentration induced by the xylazine injection. The GH levels at 15-50 min after the simultaneous injection of xylazine and atipamezole were significantly (P<0.05) lower than the corresponding values in the animals given xylazine alone. The area under the GH response curve for 120 min after the simultaneous injection of xylazine and atipamezole was significantly (P<0.05) smaller than that for the xylazine alone. A series of five intravenous injections of 1 mg of SRIF at 10-min intervals also blunted xylazine-stimulated GH release. Atipamezole partially suppressed xylazineinduced hyperglycemia, but SRIF completely suppressed the hyperglycemia for the first 60 min after the xylazine injection and the suppression by SRIF was stronger than that by atipamezole.On the other hand, both atipamezole and SRIF failed to blunt xylazine-induced hypoinsulinemia.The present results suggest that xylazine stimulates GH release via the a2-adrenergic pathway in cattle, but the mechanism of xylazine-induced hyperglycemia remains to be determined.

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“…Since this peptide does not bind to sstr3 and sstr4, these receptor subtypes can be excluded from the SRIH-GH pathway (Patel et al 1995). On the other hand, injections of BIM 23014, a peptidyl agonist selective for sstr2 and sstr5, result in a drop in plasma GH levels in rams (Magnan et al 1992). Although the efficacy of the non-peptidyl agonists remains to be further clarified in the chicken, our results suggest that the GH-controlling role of sstr5 may only have developed during the evolution to mammals.…”

Section: Discussionmentioning

confidence: 99%

Identification of somatostatin receptors controlling growth hormone and thyrotropin secretion in the chicken using receptor subtype-specific agonists

Geris

Groef

Rohrer³

et al. 2003

Journal of Endocrinology

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Somatostatin (SRIH) functions as an endocrine mediator in processes such as growth, immune resistance and reproduction. Five SRIH receptors (sstr1-5) have been identified in mammals, where they are expressed in both the brain and peripheral tissues. To study the specific function of each receptor subtype, specific agonists (ag1-5) have been synthesized. The high degree of homology between mammalian and avian SRIH receptors suggests that these agonists might also be used in chickens. In this paper we describe two in vitro protocols (static incubation and perifusion system) to identify the SRIH receptors controlling the secretion of GH and TSH from the chicken pituitary. We found that basal GH or TSH secretion were never affected when SRIH or an agonist (1 µM) were added. SRIH diminished the GH as well as the TSH response to TSH-releasing hormone (TRH; 100 nM) in both systems. Our results have indicated that the SRIH actions at the level of the pituitary are regulated through specific receptor subtypes. In both the static and flow incubations, ag2 lowered the GH response to TRH, whereas stimulated TSH release was diminished by both ag2 and ag5. Ag3 and ag4 tended to increase rather than decrease the responsiveness of both pituitary cell types to TRH in perifusion studies. Our data have indicated that SRIH inhibits chicken pituitary function through sstr2 and sstr5. Only sstr2 seems to be involved in the control of chicken GH release, whereas both sstr2 and sstr5 inhibit induced GH secretion in mammals. The possible stimulatory action of ag3 and ag4 may point towards a species-specific function of sstr3 and sstr4.

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Acute changes in growth hormone-releasing hormone secretion after injection of BIM 23014, a long acting somatostatin analog, in rams

Cited by 38 publications

References 36 publications

Six-week treatment with hexarelin in young dogs: evaluation of the GH responsiveness to acute hexarelin or GHRH administration, and of the orexigenic effect of hexarelin

Six-week treatment with hexarelin in young dogs: evaluation of the GH responsiveness to acute hexarelin or GHRH administration, and of the orexigenic effect of hexarelin

Effects of Atipamezole, an .ALPHA.2-Adrenergic Antagonist, and Somatostatin on Xylazine-lnduced Growth Hormone Release in Calves.

Identification of somatostatin receptors controlling growth hormone and thyrotropin secretion in the chicken using receptor subtype-specific agonists

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