Growth hormone in mares and stallions: pulsatile secretion, response to growth hormone-releasing hormone, and effects of exercise, sexual stimulation, and pharmacological agents.
Abstract: Short-term patterns of growth hormone (GH) secretion and factors affecting it were studied in mares and stallions. In Exp. 1, hourly blood samples were collected from three mares and three stallions in summer and winter. Although GH concentrations varied in a pulsatile manner in all horses, there was no effect of sex or season (P greater than .1) on plasma GH concentrations and no indication of a diurnal pattern of GH secretion. In Exp. 2, 10-min blood samples were drawn for 8 h from 12 mares; after 6 h, porcine GH-releasing hormone (GHRH) was administered i.v. at 0, 45, 90, or 180 micrograms/mare (three mares per dose). Pulsatile secretion of GH occurred in all mares and averaged 2.4 +/- .3 peaks/6 h; amplitudes were variable and ranged from 2.6 to 74.4 ng/mL. Eight of nine mares responded within 20 min to GHRH injection, but there was no difference (P greater than .1) among the three doses tested. In Exp. 3, plasma GH concentrations in stallions increased (P less than .05) 8- to 10-fold after 5 min of acute physical exercise or exposure to an estrual mare. Restraint via a twitch (5 min) and epinephrine administration (3 mg i.v.) also increased (P less than .05) plasma GH concentrations by approximately fourfold. In Exp. 4 and 5, administration of either .4, 2, or 10 mg of thyrotropin-releasing hormone (TRH) or 100 or 500 mg of sulpiride (a dopamine receptor antagonist) increased (P less than .01) plasma prolactin concentrations but had no effect (P greater than .1) on GH concentrations during the same period of time.(ABSTRACT TRUNCATED AT 250 WORDS)
Publication Date: 1992-04-11 PubMed ID: 1582951DOI: 10.2527/1992.7041201xGoogle Scholar: Lookup
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- Journal Article
Summary
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This research article explores how various factors such as exercise, sexual stimulation, and certain drugs can affect the secretion of growth hormone (GH) in mares and stallions, and sees no significant influence of sex or seasonality on GH concentrations. The researchers also examined the animals’ response to the administration of growth hormone-releasing hormone (GHRH) and found varying, pulsatile secretion patterns of GH.
Study Design and Methods
- The research was conducted through a series of experiments. In Experiment 1, the researchers took hourly blood samples from three mares and three stallions in both summer and winter seasons. Measurments of GH concentration in the blood were recorded.
- In Experiment 2, blood samples were drawn every 10 minutes for a duration of 8 hours from 12 mares. After 6 hours, the mares were administered varying doses of porcine GH-releasing hormone (GHRH) intravenously.
- In Experiment 3, the investigators studied the effects of short bouts of physical exercise or exposure to an estrus mare on plasma GH concentrations in stallions. They measured the fluctuations in GH concentrations after physical restraint and administration of epinephrine.
- Experiment 4 and 5 were designed to study the effects of thyrotropin-releasing hormone (TRH) and sulpiride, a dopamine receptor antagonist, on plasma prolactin and GH concentrations.
Key Findings
- GH concentrations varied in a pulsatile manner in all horses.
- There was no significant effect on GH concentrations based on sex or season.
- Pulsatile secretion of GH occurred in all mares following administration of GHRH, showing varying amplitude range.
- Physical exercise and sexual stimulation caused significant increases in plasma GH concentrations in stallions.
- Restraint using a twitch and administration of epinephrine also triggered a significant increase in plasma GH concentrations.
- Administration of TRH or sulpiride boosted plasma prolactin concentrations. However, they had no significant effect on GH concentrations.
Conclusions
- The research establishes that exercise, sexual stimulation, and certain pharmacological agents can significantly affect the secretion of GH in mares and stallions.
- However, sex or season seems to have no substantial effect on GH secretion amongst the sample group.
- The response of mares to GHRH injection was variable but had no significant relationship with the dosage of GHRH administered.
- The two tested pharmacological agents notably affected plasma prolactin levels while leaving GH concentrations unchanged.
Cite This Article
APA
Thompson DL, Rahmanian MS, DePew CL, Burleigh DW, DeSouza CJ, Colborn DR.
(1992).
Growth hormone in mares and stallions: pulsatile secretion, response to growth hormone-releasing hormone, and effects of exercise, sexual stimulation, and pharmacological agents.
J Anim Sci, 70(4), 1201-1207.
https://doi.org/10.2527/1992.7041201x Publication
Researcher Affiliations
- Animal Science Department, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803.
MeSH Terms
- Animals
- Circadian Rhythm
- Female
- Growth Hormone / blood
- Growth Hormone / metabolism
- Growth Hormone-Releasing Hormone / pharmacology
- Horses / growth & development
- Horses / metabolism
- Male
- Physical Exertion / physiology
- Pituitary Gland, Anterior / drug effects
- Pituitary Gland, Anterior / metabolism
- Prolactin / blood
- Regression Analysis
- Seasons
- Sex Characteristics
- Sexual Behavior, Animal / physiology
- Sulpiride / pharmacology
- Thyrotropin-Releasing Hormone / pharmacology
Citations
This article has been cited 2 times.- Ferlazzo A, Cravana C, Fazio E, Medica P. The different hormonal system during exercise stress coping in horses. Vet World 2020 May;13(5):847-859.
- Borromeo V, Abbate F, Berrini A, Bartolone A, Secchi C. Monoclonal antibody capture fluorometric enzyme-linked immunosorbent assay for detection of equine growth hormone in plasma. Vet Res Commun 2005 Aug;29 Suppl 2:173-6.
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