Effect of circulating growth hormone on muscle IGF-I protein concentration in female mice with growth hormone receptor gene disruption

William J. Kraemer, Jakob L. Vingren, Mark D. Schuenke, John J. Kopchick, Jeff S. Volek, Maren S. Fragala, Keijo Häkkinen, Jen-Ho, Gwendolyn A. Thomas, Robert S. Staron

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Abstract

Growth hormone (GH) is a potent secretague for circulating insulin-like growth factor-I (IGF-I). The purpose of this study was to examine the effect of circulating GH on muscle IGF-I protein expression using GH transgenic animal models. Three different models were used: mice that overexpress bovine GH (bGH; n = 10), mice without a functional GH receptor (GHR-/-; n = 10), and wildtype mice (n = 10). All mice were 16-week old females and each group differed in their basic phenotypic characteristics. Immediately after euthanization the triceps surae muscle group (soleus, plantaris, and gastrocnemius muscles) was removed. IGF-I was extracted from the muscle with an acid-ethanol solution (12.5% 2N hydrochloric acid and 87.5% ethanol, pH 1.5) followed by neutralization with Tris-base and subsequently quantified using a radioimmunoassay. Analysis revealed that bGH mice had significantly greater muscle IGF-I protein expression compared to GHR-/- and wildtype mice. No difference in IGF-I protein concentration was found between GHR-/- and wildtype animals. This study found that overexpression of GH leading to high circulating GH concentrations increase muscle IGF-I protein expression. However, the absence of a functional GHR did not affect muscle IGF-I protein expression compared to wildtype despite high circulating levels of GH and low circulating levels of IGF-I. In conclusion, it appears that at rest high circulating levels of GH augment muscle IGF-I protein expression only in the presence of an intact GHR but that the absence of a functional GH receptor does not affect basal levels of muscle IGF-I protein in female mice.

Original languageEnglish
Pages (from-to)242-244
Number of pages3
JournalGrowth Hormone and IGF Research
Volume19
Issue number3
DOIs
Publication statusPublished - 2009 Jun 1

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Keywords

  • Endocrine
  • Hormone
  • Insulin-like growth factor-I
  • Knockout
  • Over expression

ASJC Scopus subject areas

  • Endocrinology, Diabetes and Metabolism
  • Endocrinology

Cite this

Kraemer, W. J., Vingren, J. L., Schuenke, M. D., Kopchick, J. J., Volek, J. S., Fragala, M. S., Häkkinen, K., Jen-Ho, Thomas, G. A., & Staron, R. S. (2009). Effect of circulating growth hormone on muscle IGF-I protein concentration in female mice with growth hormone receptor gene disruption. Growth Hormone and IGF Research, 19(3), 242-244. https://doi.org/10.1016/j.ghir.2008.10.006