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

• Published in: Molecular and cellular endocrinology 1995-09, Vol.113 (2), p.215-223
• Main Authors: Dubuis, J.-M., Deal, C.L., Van Vliet, G.
• Format: Article
• Language: English
• Subjects: Animals; Base Sequence; Binding protein; Blotting, Northern; Female; Growth; Growth hormone; Growth Hormone - metabolism; Growth Hormone - pharmacology; Growth hormone receptor; 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; Insulin-like growth factor-I; Liver - metabolism; Male; Molecular Sequence Data; Obesity (Zucker rat); Obesity - physiopathology; Rats; Rats, Zucker; Receptors, Somatotropin - genetics; RNA, Messenger - metabolism
• ISSN: 0303-7207; 1872-8057
• DOI: 10.1016/0303-7207(95)03631-G

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 RNA/GHR mRNA ratios associated with obesity were sex-specific. In both genders, IGFBP-1 and IGFBP-3 mRNAs were decreased in the obese. We conclude 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.