Low doses of estradiol partly inhibit release of GH in sheep without affecting basal levels

Andy Hudmon, G. Davenport, E. S. Coleman, J. L. Sartin

Research output: Contribution to journalArticle

3 Citations (Scopus)

Abstract

Estradiol increases basal growth hormone (GH) concentrations in sheep and cattle. This study sought to determine the effects of estradiol on GH-releasing hormone (GRH)-stimulated GH release in sheep. Growth hormone secretory characteristics, the GH response to GRH, and steady-state GH mRNA concentrations were determined in castrated male lambs treated with 2 different doses of estradiol 17-β for a 28-d experimental period. Although no differences between treatments in mean GH, basal GH, or GH pulse number were observed after 28 d of estradiol treatment, GH pulse amplitude was greater (P < 0.05) in the 2.00-cm implant-treated animals than in the control and 0.75-cm implant group. The effect of estradiol treatment on GRH-stimulated GH release revealed differences between the control and estradiol-treated animals (P < 0.05). The 15-min GH responses to 0.075 μg/kg hGRH in the control, 0.75-cm, and 2.00-cm implant groups, respectively, were 76 ± 10, 22.6 ± 2.1, and 43.6 ± 15.0 ng/mL. Growth hormone mRNA content was determined for pituitary glands from the different treatment groups, and no differences in steady-state GH mRNA levels were observed. There were no differences in the mean plasma concentrations of IGF-I, cortisol, T3, or T4 from weekly samples. Growth hormone release from cultured ovine pituitary cells from control sheep was not affected by estradiol after 72 h or in a subsequent 3-h incubation with estradiol combined with GRH. These data suggest that estradiol has differing actions on basal and GRH-stimulated GH concentrations in plasma, but the increase in pulse amplitude does not represent an increased pituitary sensitivity to GRH.

Original languageEnglish
Pages (from-to)181-187
Number of pages7
JournalDomestic Animal Endocrinology
Volume37
Issue number3
DOIs
StatePublished - Oct 2009

Fingerprint

somatotropin
Growth Hormone
estradiol
Estradiol
Sheep
sheep
dosage
Growth Hormone-Releasing Hormone
hormones
Hormones
Messenger RNA
somatoliberin
Pituitary Gland
L-thyroxine
Insulin-Like Growth Factor I
pituitary gland
triiodothyronine
insulin-like growth factor I
Hydrocortisone
cortisol

Keywords

  • Estrogen
  • Growth
  • Growth hormone

ASJC Scopus subject areas

  • Animal Science and Zoology
  • Endocrinology
  • Food Animals

Cite this

Low doses of estradiol partly inhibit release of GH in sheep without affecting basal levels. / Hudmon, Andy; Davenport, G.; Coleman, E. S.; Sartin, J. L.

In: Domestic Animal Endocrinology, Vol. 37, No. 3, 10.2009, p. 181-187.

Research output: Contribution to journalArticle

Hudmon, Andy ; Davenport, G. ; Coleman, E. S. ; Sartin, J. L. / Low doses of estradiol partly inhibit release of GH in sheep without affecting basal levels. In: Domestic Animal Endocrinology. 2009 ; Vol. 37, No. 3. pp. 181-187.
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