The growth hormone (GH)-independent growth of the obese Zucker rat is not due to increased levels of GH receptor messenger RNA in the liver

Mol Cell Endocrinol. 1995 Sep 22;113(2):215-23. doi: 10.1016/0303-7207(95)03631-g.

Abstract

Obese Zucker rats maintain normal rates of linear growth and circulating concentrations of insulin-like growth factor-I (IGF-I) and of IGF-binding protein-3 (IGFBP-3) in spite of low GH secretion. The mechanisms underlying this GH-independent growth in obesity are unknown. To assess whether the liver expression of the GH receptor (GHR) messenger RNA (mRNA) is increased and/or if the liver expression of IGFBP-3 mRNA is maintained in the obese, Zucker rats of both genders and phenotypes (four groups, n = 6/group) were studied at 12 weeks of age. By Northern analysis, mRNA levels for GHR and GHBP were not increased in obese rats compared to their sex-matched lean littermates; the expression of these two transcripts was sexually dimorphic and the changes in GHBP mRNA/GHR mRNA ratios associated with obesity were sex-specific. In both genders, IGFBP-1 and IGFBP-3 mRNAs were decreased in the obese. We concluded that the GH-independent growth of obese Zucker rats is not due to increased GHR mRNA or to maintained IGFBP-3 mRNA levels in the liver.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Base Sequence
  • Blotting, Northern
  • Female
  • Growth Hormone / metabolism
  • Growth Hormone / pharmacology*
  • Growth*
  • Insulin-Like Growth Factor Binding Protein 1 / genetics
  • Insulin-Like Growth Factor Binding Protein 2 / genetics
  • Insulin-Like Growth Factor Binding Protein 3 / genetics
  • Insulin-Like Growth Factor Binding Protein 3 / metabolism
  • Insulin-Like Growth Factor Binding Protein 4 / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Liver / metabolism*
  • Male
  • Molecular Sequence Data
  • Obesity / physiopathology*
  • RNA, Messenger / metabolism*
  • Rats
  • Rats, Zucker
  • Receptors, Somatotropin / genetics*

Substances

  • Insulin-Like Growth Factor Binding Protein 1
  • Insulin-Like Growth Factor Binding Protein 2
  • Insulin-Like Growth Factor Binding Protein 3
  • Insulin-Like Growth Factor Binding Protein 4
  • RNA, Messenger
  • Receptors, Somatotropin
  • Insulin-Like Growth Factor I
  • Growth Hormone