title: 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.
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.
authors.affiliation: Unit on Reproductive and Developmental Biology, Sainte-Justine Hospital, Montreal, Quebec, Canada.
authors.forename: J M
authors.initials: JM
authors.lastname: Dubuis
authors.forename: C L
authors.initials: CL
authors.lastname: Deal
authors.forename: G
authors.initials: G
authors.lastname: Van Vliet
mesh_terms: D000818:Animals; D001483:Base Sequence; D015152:Blotting, Northern; D005260:Female; D006128:Growth; D013006:Growth Hormone / Q000378:metabolism / Q000494:pharmacology*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000235:genetics; D018971:Insulin-Like Growth Factor Binding Protein 2 / Q000235:genetics; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000235:genetics / Q000378:metabolism; D018974:Insulin-Like Growth Factor Binding Protein 4 / Q000235:genetics; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D008099:Liver / Q000378:metabolism*; D008297:Male; D008969:Molecular Sequence Data; D009765:Obesity / Q000503:physiopathology*; D012333:RNA, Messenger / Q000378:metabolism*; D051381:Rats; D011924:Rats, Zucker; D011986:Receptors, Somatotropin / Q000235:genetics*
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1; D018971:Insulin-Like Growth Factor Binding Protein 2; D018972:Insulin-Like Growth Factor Binding Protein 3; D018974:Insulin-Like Growth Factor Binding Protein 4; D012333:RNA, Messenger; D011986:Receptors, Somatotropin; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone