Dubuis J M, Deal C L, Van Vliet G
Unit on Reproductive and Developmental Biology, Sainte-Justine Hospital, Montreal, Quebec, Canada.
Mol Cell Endocrinol. 1995 Sep 22;113(2):215-23. 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 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.
尽管生长激素（GH）分泌水平较低，但肥胖的Zucker大鼠仍保持正常的线性生长速度以及胰岛素样生长因子-I（IGF-I）和IGF结合蛋白-3（IGFBP-3）的循环浓度。肥胖状态下这种不依赖GH的生长机制尚不清楚。为了评估肥胖的Zucker大鼠肝脏中生长激素受体（GHR）信使核糖核酸（mRNA）的表达是否增加，以及/或者IGFBP-3 mRNA的肝脏表达是否维持正常，我们研究了12周龄的不同性别和表型的Zucker大鼠（四组，每组n = 6）。通过Northern分析，与性别匹配的瘦型同窝仔鼠相比，肥胖大鼠中GHR和GHBP的mRNA水平并未增加；这两种转录本的表达具有性别差异，且与肥胖相关的GHBP mRNA/GHR mRNA比值变化具有性别特异性。在两种性别中，肥胖大鼠的IGFBP-1和IGFBP-3 mRNA均降低。我们得出结论，肥胖的Zucker大鼠不依赖GH的生长并非由于肝脏中GHR mRNA增加或IGFBP-3 mRNA水平维持不变。
