Iino S, Horiguchi K, Nojyo Y
Department of Morphological and Physiological Sciences, University of Fukui Faculty of Medical Sciences, Eiheiji, Fukui 910-1193, Japan.
Neuroscience. 2008 Mar 18;152(2):437-48. doi: 10.1016/j.neuroscience.2007.12.044. Epub 2008 Jan 12.
Nitric oxide (NO) is a major signaling molecule in the gastrointestinal tract, and released NO inhibits muscular contraction. The actions of NO are mediated by stimulation of soluble guanylate cyclase (sGC, NO-sensitive GC) and a subsequent increase in cGMP concentration. To elucidate NO targets in the gastrointestinal musculature, we investigated the immunohistochemical localization of the beta1 and alpha1 subunits of sGC and the distribution of neuronal NO synthase (nNOS) -containing nerves in the guinea-pig gastrointestinal tract. Distinct immunoreactivity for sGCbeta1 and sGCalpha1 was observed in the interstitial cells of Cajal (ICC), fibroblast-like cells (FLC) and enteric neurons in the musculature. Double immunohistochemistry using anti-c-Kit antibody and anti-sGCbeta1 antibody revealed sGCbeta1 immunoreactivity in almost all intramuscular ICC throughout the entire gastrointestinal tract. Immunoelectron microscopy revealed that sGCbeta1-immunopositive cells possessed some of the criteria for intramuscular ICC: presence of caveolae; frequently associated with nerve bundles; and close contact with smooth muscle cells. sGCbeta1-immunopositive ICC were closely apposed to nNOS-containing nerve fibers in the muscle layers. Immunohistochemical and immunoelectron microscopical observations revealed that FLC in the musculature also showed sGCbeta1 immunoreactivity. FLC were often associated with nNOS-immunopositive nerve fibers. In the myenteric layer, almost all myenteric ganglia contained nNOS-immunopositive nerve cells and were surrounded by myenteric ICC and FLC. Myenteric ICC in the large intestine and FLC in the entire gastrointestinal tract showed sGCbeta1 immunoreactivity in the myenteric layer. Smooth muscle cells in the stomach and colon showed weak sGCbeta1 immunoreactivity, and those in the muscularis mucosae and vasculature also showed evident immunoreactivity. These data suggest that ICC are primary targets for NO released from nNOS-containing enteric neurons, and that some NO signals are received by FLC and smooth muscle cells in the gastrointestinal tract.
一氧化氮（NO）是胃肠道中的一种主要信号分子，释放出的NO可抑制肌肉收缩。NO的作用是通过刺激可溶性鸟苷酸环化酶（sGC，NO敏感型GC）并随后增加cGMP浓度来介导的。为了阐明胃肠道肌肉组织中的NO靶点，我们研究了sGC的β1和α1亚基的免疫组织化学定位以及豚鼠胃肠道中含神经元型一氧化氮合酶（nNOS）神经的分布。在肌肉组织中的 Cajal间质细胞（ICC）、成纤维细胞样细胞（FLC）和肠神经元中观察到了sGCβ1和sGCalpha1的明显免疫反应性。使用抗c-Kit抗体和抗sGCβ1抗体进行的双重免疫组织化学显示，在整个胃肠道的几乎所有肌内ICC中都有sGCβ1免疫反应性。免疫电子显微镜显示，sGCβ1免疫阳性细胞具有肌内ICC的一些特征：存在小窝；经常与神经束相关；并与平滑肌细胞紧密接触。sGCβ1免疫阳性的ICC与肌肉层中含nNOS的神经纤维紧密相邻。免疫组织化学和免疫电子显微镜观察显示，肌肉组织中的FLC也显示出sGCβ1免疫反应性。FLC经常与nNOS免疫阳性神经纤维相关。在肌间层，几乎所有肌间神经节都含有nNOS免疫阳性神经细胞，并被肌间ICC和FLC包围。大肠中的肌间ICC和整个胃肠道中的FLC在肌间层显示出sGCβ1免疫反应性。胃和结肠中的平滑肌细胞显示出较弱的sGCβ1免疫反应性，而黏膜肌层和脉管系统中的平滑肌细胞也显示出明显的免疫反应性。这些数据表明，ICC是含nNOS的肠神经元释放的NO的主要靶点，并且胃肠道中的一些NO信号被FLC和平滑肌细胞接收。
