Zhang W H, Beaudet A, Tannenbaum G S
Neuropeptide Physiology Laboratory, McGill University-Montreal Children's Hospital Research Institute, Montreal, Quebec, Canada.
J Neuroendocrinol. 1999 Feb;11(2):129-36. doi: 10.1046/j.1365-2826.1999.00295.x.
The pattern of growth hormone (GH) secretion and rate of somatic growth are markedly sexually dimorphic, but the underlying neuroendocrine mechanisms are far from clear. In the present study, we tested the hypothesis that the sexual dimorphism of GH secretion may be due to gender-related differences in the transduction of somatostatin's actions in brain and/or pituitary. To accomplish this, we compared the distributional pattern and level of expression of two somatostatin receptor subtypes, sst1 and sst2, in the brain and pituitary of adult male and female rats by in-situ hybridization using 35S-labelled antisense riboprobes. In the brain, the hybridization pattern and labelling density of sst1 and sst2 mRNA-expressing cells, as revealed by computer-assisted image analysis, in areas including the cerebral cortex, medial habenula (MHb) and ventromedial hypothalamic nucleus (VMN), were similar in male and female rats. In contrast, there was a marked sex-related difference in sst1 expression in the arcuate nucleus of the hypothalamus; both the number and labelling density of sst1 mRNA-expressing cells were two- to threefold greater in males than in females and this significant increase was homogenous throughout the rostrocaudal extent of the nucleus. No gender-related differences in arcuate sst2 mRNA levels were found. At the level of the anterior pituitary, the labelling density of sst2 mRNA in males was significantly higher than that of females. No sex-related difference in pituitary sst1 mRNA was observed. These results demonstrate a sexual dimorphism in the expression of two somatostatin receptor subtypes, sst1 and sst2, at the level of the arcuate nucleus and anterior pituitary, respectively. Such dimorphism suggests a differential involvement of sst1 and sst2 in GH regulation with respect to gender, and may imply roles for sst2 and sst1 in transducing somatostatin's actions on pituitary somatotrophs and GH-releasing hormone-containing arcuate neurones, respectively, to generate the lower basal and higher GH pulse levels characteristic of the male rat.
生长激素（GH）的分泌模式和体细胞生长速率存在明显的性别差异，但其潜在的神经内分泌机制尚不清楚。在本研究中，我们检验了以下假设：GH分泌的性别差异可能是由于大脑和/或垂体中生长抑素作用转导的性别相关差异所致。为实现这一目标，我们使用35S标记的反义核糖探针，通过原位杂交比较了成年雄性和雌性大鼠大脑和垂体中两种生长抑素受体亚型sst1和sst2的分布模式和表达水平。在大脑中，通过计算机辅助图像分析显示，在包括大脑皮层、内侧缰核（MHb）和腹内侧下丘脑核（VMN）等区域，sst1和sst2 mRNA表达细胞的杂交模式和标记密度在雄性和雌性大鼠中相似。相反，下丘脑弓状核中sst1的表达存在明显的性别相关差异；表达sst1 mRNA的细胞数量和标记密度在雄性中比雌性高两到三倍，并且这种显著增加在整个核的前后范围内是均匀的。未发现弓状核sst2 mRNA水平存在性别相关差异。在前脑垂体水平，雄性中sst2 mRNA的标记密度显著高于雌性。未观察到垂体sst1 mRNA存在性别相关差异。这些结果分别证明了两种生长抑素受体亚型sst1和sst2在弓状核和前脑垂体水平的表达存在性别差异。这种差异表明sst1和sst2在GH调节中对性别的参与不同，可能分别意味着sst2和sst1在转导生长抑素对垂体生长激素细胞和含生长激素释放激素的弓状神经元的作用，以产生雄性大鼠较低的基础GH水平和较高的GH脉冲水平方面发挥作用。
