Hurley D L, Wee B E, Phelps C J
Department of Cell and Molecular Biology, Tulane University, New Orleans, LA 70118, USA.
Neuroendocrinology. 1997 Feb;65(2):98-106. doi: 10.1159/000127169.
Lifelong deficiency of growth hormone (GH) in spontaneous or transgenic dwarf mice has been shown to be accompanied by reduced hypophysiotropic somatostatin (somatotropin release-inhibiting hormone, SRIH) expression in hypothalamic anterior periventricular nucleus (PeN). However, the postnatal developmental pattern of SRIH expression in the absence of GH is unknown. Therefore, SRIH mRNA levels in GH-deficient Ames dwarf (df/df) mice and normal (DF/?) littermates were determined both in adults, to compare with other GH-deficient models, and at selected days of postnatal development, to determine the effects of GH deficiency on SRIH neuron development. DF/? and df/df mice of both sexes at postnatal ages 1, 3, 7, 14, 21 and 60 days (adult) were examined. In situ hybridization and image analysis were used to quantify the relative abundance of total SRIH mRNA in the PeN, and SRIH mRNA per cell was determined in PeN and medial basal hypothalamus (MBH). In adult df/df mice, total PeN SRIH mRNA was 45% (p < 0.05) of that in DF/? littermates, which is consistent with studies of other GH-deficient dwarf mice. In developing animals, SRIH expression in the PeN of DF/? mice began at 3 days of age and increased at subsequent ages to reach adult levels. In df/df mice, PeN SRIH mRNA levels at 60 days were significantly greater than at 1-21 days of age (p < 0.05). However, levels were not different over 1-21 days of age, and were consistently lower in df/df than DF/? mice. The difference in total PeN SRIH mRNA between df/df and DF/? mice was statistically significant at 7 days, and at each subsequent age. There were no differences between DF/? and df/df mice in the number of grains per cell in either PeN or MBH at any age. Thus, the reduced total hypophysiotropic SRIH mRNA in GH-deficient Ames dwarf mice appears developmentally shortly after initial detectability of SRIH in the PeN. Because SRIH mRNA per cell was the same for DF/? and df/df mice, the decreased total mRNA in dwarfs suggested reduced SRIH cell numbers in PeN, which was corroborated by immunocytochemical findings. The reduction of SRIH in df/df mice at 7 days of age suggests that GH production during embryonic or very early postnatal development is important to activation of PeN SRIH transcription.
自发性或转基因侏儒小鼠中生长激素（GH）的终身缺乏已被证明伴随着下丘脑室周前核（PeN）中促垂体生长抑素（生长激素释放抑制激素，SRIH）表达的降低。然而，在缺乏GH的情况下SRIH表达的出生后发育模式尚不清楚。因此，我们测定了GH缺乏的艾姆斯侏儒（df/df）小鼠和正常（DF/?）同窝小鼠在成年期（以便与其他GH缺乏模型进行比较）以及出生后发育的选定天数时的SRIH mRNA水平，以确定GH缺乏对SRIH神经元发育的影响。对出生后1、3、7、14、21和60天（成年）的雌雄DF/?和df/df小鼠进行了检查。采用原位杂交和图像分析来量化PeN中总SRIH mRNA的相对丰度，并测定PeN和下丘脑内侧基底部（MBH）中每个细胞的SRIH mRNA。在成年df/df小鼠中，PeN中总SRIH mRNA是DF/?同窝小鼠的45%（p<0.05），这与其他GH缺乏侏儒小鼠的研究结果一致。在发育中的动物中，DF/?小鼠PeN中的SRIH表达在3日龄开始，并在随后的年龄增加至成年水平。在df/df小鼠中，60天时PeN的SRIH mRNA水平显著高于1至21日龄时（p<0.05）。然而，在1至21日龄期间水平没有差异，并且df/df小鼠中的水平始终低于DF/?小鼠。df/df和DF/?小鼠之间PeN中总SRIH mRNA的差异在7天时具有统计学意义，并且在随后的每个年龄都是如此。在任何年龄，DF/?和df/df小鼠在PeN或MBH中每个细胞的颗粒数均无差异。因此，GH缺乏的艾姆斯侏儒小鼠中促垂体SRIH mRNA总量的降低似乎在PeN中首次检测到SRIH后不久就已在发育过程中出现。由于DF/?和df/df小鼠每个细胞的SRIH mRNA相同，侏儒小鼠中总mRNA的降低表明PeN中SRIH细胞数量减少，免疫细胞化学结果证实了这一点。df/df小鼠在7日龄时SRIH的减少表明胚胎期或出生后极早期的GH产生对于激活PeN SRIH转录很重要。
