Effects of growth hormone-releasing peptides in healthy dogs and in dogs with pituitary-dependent hyperadrenocorticism

Bhatti, Sofie; Vliegher, S.P De; Ham, Luc Van; Kooistra, H.S.

doi:10.1016/s0303-7207(02)00293-9

Cited by 15 publications

(13 citation statements)

References 39 publications

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“…This may be due to ageing [49], since the dogs in our study were considerably older than those in the study of Meij et al [22]. In addition, a relatively high plasma GH level before suprapituitary stimulation in one of the dogs, probably explained by sampling during a GH pulse, had a substantial influence on basal plasma GH concentration.…”

Section: Discussionmentioning

confidence: 52%

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

Beijerink

Bhatti

Okkens

et al. 2007

Domestic Animal Endocrinology

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The aim of this study was to investigate the effects of treatment with medroxyprogesterone acetate (MPA) on canine adenohypophyseal function. Five Beagle bitches were treated with MPA (10 mg/kg, every 4 weeks) and their adenohypophyseal function was assessed in a combined adenohypophyseal function test. Four hypophysiotropic hormones (CRH, GHRH, GnRH, and TRH) were administered before and 2, 5, 8, and 11 months after the start of MPA treatment, and blood samples for determination of the plasma concentrations of ACTH, cortisol, GH, IGF-1, LH, FSH, prolactin, ␣-MSH, and TSH were collected at −15, 0, 5, 10, 20, 30, and 45 min after suprapituitary stimulation.MPA successfully prevented the occurrence of estrus, ovulation, and a subsequent luteal phase. MPA treatment did not affect basal and GnRH-induced plasma LH concentrations. The basal plasma FSH concentration was significantly higher at 2 months after the start of MPA treatment than before or at 5, 8, and 11 months after the start of treatment. The maximal FSH increment and the AUC for N.J. Beijerink et al. / Domestic Animal Endocrinology xxx (2006) xxx-xxxmonths of MPA treatment. Differences in mean basal plasma GH concentrations before and during treatment were not significant, but MPA treatment resulted in significantly elevated basal plasma IGF-1 concentrations at 8 and 11 months. MPA treatment did not affect basal and stimulated plasma ACTH concentrations, with the exception of a decreased AUC for ACTH at 11 months. In contrast, the maximal cortisol increment and the AUC for cortisol after suprapituitary stimulation were significantly lower during MPA treatment than prior to treatment. MPA treatment did not affect basal plasma concentrations of prolactin, TSH, and ␣-MSH, with the exception of slightly increased basal plasma TSH concentrations at 8 months of treatment. MPA treatment did not affect TRH-induced plasma concentrations of prolactin and TSH.In conclusion, the effects of chronic MPA treatment on adenohypophyseal function included increased FSH secretion, unaffected LH secretion, activation of the mammary GH-induced IGF-I secretion, slightly activated TSH secretion, suppression of the hypothalamic-pituitary-adrenocortical axis, and unaffected secretion of prolactin and ␣-MSH.

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Section: Discussionmentioning

confidence: 52%

Adenohypophyseal function in bitches treated with medroxyprogesterone acetate

Beijerink

Bhatti

Okkens

et al. 2007

Domestic Animal Endocrinology

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“…Until now, the effect of ageing on the GH responsiveness to ghrelin has not been studied in the dog. Preliminary results on the effects of GHSs on GH, ACTH, and cortisol concentrations in old dogs have however been reported earlier (Bhatti et al, 2002).…”

Section: Introductionmentioning

confidence: 99%

Effects of growth hormone secretagogues on the release of adenohypophyseal hormones in young and old healthy dogs

Bhatti

Duchateau

Ham

et al. 2006

The Veterinary Journal

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The effects of three growth hormone secretagogues (GHSs), ghrelin, growth hormone-releasing peptide-6 (GHRP-6), and growth hormone-releasing hormone (GHRH), on the release of adenohypophyseal hormones, growth hormone (GH), adrenocorticotropic hormone (ACTH), thyroid-stimulating hormone (TSH), luteinising hormone (LH), prolactin (PRL) and on cortisol were investigated in young and old healthy Beagle dogs.Ghrelin proved to be the most potent GHS in young dogs, whereas in old dogs GHRH administration was associated with the highest plasma GH concentrations. The mean plasma GH response after administration of ghrelin was significantly lower in the old dogs compared with the young dogs. The mean plasma GH concentration after GHRH and GHRP-6 administration was lower in the old dogs compared with the young dogs, but this difference did not reach statistical significance. In both age groups, the GHSs were specific for GH release as they did not cause significant elevations in the plasma concentrations of ACTH, cortisol, TSH, LH, and PRL. It is concluded that in young dogs, ghrelin is a more powerful stimulator of GH release than either GHRH or GHRP-6. Ageing is associated with a decrease in GH-releasing capacity of ghrelin, whereas this decline is considerably lower for GHRH or GHRP-6.

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“…31,72,78,79 The effect of ghrelin on PRL secretion is independent of gender and age and likely results from direct stimulation of somatomammotrophs. 72,78,80,81 In dogs 28,29 and rats, 8 synthetic GHSs do not stimulate PRL release. This species-related difference may be explained by differences in the number of somatomammotrophs in various species, with humans having a high proportion of those cells.…”

Section: 74mentioning

confidence: 99%

“…8,21,[27][28][29]31,51,[70][71][72][73] The GH-releasing activity of ghrelin is greater in vivo than in vitro because ghrelin and GHRH act synergistically, consistent with the fact that their actions are at least partially mediated via different mechanisms.…”

Section: Endocrine Effects Of Ghrelinmentioning

confidence: 99%