Nass R, Gilrain J, Anderson S, Gaylinn B, Dalkin A, Day R, Peruggia M, Thorner M O
Department of Medicine, University of Virginia, Charlottesville 22908, USA.
Endocrinology. 2000 Jun;141(6):2084-9. doi: 10.1210/endo.141.6.7503.
Synthetic GH secretagogues (GHSs) act via a receptor (GHS-R) distinct from that of GH-releasing hormone. The GHS-R has been cloned from the pituitary and is expressed not only in the pituitary but also in specific areas of the brain, including the hypothalamus. Recent studies suggest that hypothalamic GHS-R expression is regulated by GH. This study was designed to investigate whether pituitary GHS-R expression is modulated by GH. Female Wistar-Furth rats were injected sc with either saline (control) or GC tumor cells (GC) that secrete rat GH. The tumors were allowed to develop for 1-4 weeks. At weeks 1-4, control (n = 4-8) and GC rats (n = 3-8) were killed. Pituitary GHS-R messenger RNA (mRNA) was measured by a quantitative competitive PCR assay. The endogenous GHS-R mRNA levels were measured by determining the amount of competitive template RNA required to produce equimolar amounts of native and competitive template PCR products. The mean log plasma GH levels were significantly greater in the GC rat group than in the control group at weeks 2, 3, and 4. At these times, the mean log pituitary GHS-R mRNA contents were significantly lower in the GC rat group than in the control group. No relationship could be established between log estradiol levels and GHS-R levels. These data indicate that pituitary GHS-R expression is modulated by GH.
合成生长激素促分泌素（GHSs）通过一种不同于生长激素释放激素的受体（GHS-R）发挥作用。GHS-R已从垂体中克隆出来，不仅在垂体中表达，还在大脑的特定区域表达，包括下丘脑。最近的研究表明，下丘脑GHS-R的表达受生长激素调节。本研究旨在调查垂体GHS-R的表达是否受生长激素调节。给雌性Wistar-Furth大鼠皮下注射生理盐水（对照组）或分泌大鼠生长激素的GC肿瘤细胞（GC组）。让肿瘤生长1至4周。在第1至4周，处死对照组（n = 4 - 8）和GC组大鼠（n = 3 - 8）。通过定量竞争PCR测定法测量垂体GHS-R信使核糖核酸（mRNA）。通过确定产生等摩尔量的天然和竞争模板PCR产物所需的竞争模板RNA量来测量内源性GHS-R mRNA水平。在第2、3和4周时，GC组大鼠的平均对数血浆生长激素水平显著高于对照组。此时，GC组大鼠的平均对数垂体GHS-R mRNA含量显著低于对照组。雌二醇水平对数与GHS-R水平之间未发现相关性。这些数据表明垂体GHS-R的表达受生长激素调节。
