The carotid body (CB) is a multipurpose metabolic sensor that acts to initiate cardiorespiratory reflex adjustments to maintain homeostasis of blood-borne chemicals. Emerging evidence suggests that nitric oxide increases the CB chemosensory activity and this enhanced peripheral chemoreflex sensitivity contributes to sympathoexcitation and consequent pathology. The aim of this study was to examine by means of NADPH-diaphorase histochemistry and nitric oxide synthase (NOS) immunohistochemistry the presence and distribution of nitrergic structures in the CB of spontaneously hypertensive rats (SHRs) and to compare their expression patterns to that of age-matched normotensive Wistar rats (NWRs). Histochemistry revealed that the chemosensory glomus cells were NADPH-d-negative but were encircled by fine positive varicosities, which were also dispersed in the stroma around the glomeruli. The NADPH-d-reactive fibers showed the same distributional pattern in the CB of SHRs, however their staining activity was weaker when compared with NWRs. Thin periglomerular, intraglomerular and perivascular varicose fibers, but not glomus or sustentacular cells in the hypertensive CB, constitutively expressed two isoforms of NOS, nNOS and eNOS. In addition, clusters of glomus cells and blood vessels in the CB of SHRs exhibited moderate immunoreactivity for the third known NOS isoenzyme, iNOS. The present study demonstrates that in the hypertensive CB nNOS and eNOS protein expression shows statistically significant down-regulation whereas iNOS expression is up-regulated in the glomic tissue compared to normotensive controls. Our results suggest that impaired NO synthesis could contribute to elevated blood pressure in rats via an increase in chemoexcitation and sympathetic nerve activity in the CB.

中文翻译：

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自发性高血压大鼠颈动脉硝化能结构的组织化学和免疫组化定位。

颈动脉体（CB）是一种多功能代谢传感器，可启动心肺反射调节以维持血液中化学物质的稳态。越来越多的证据表明，一氧化氮会增加CB的化学感应活性，而这种增强的外周化学反射敏感性会导致交感神经兴奋和随之而来的病理。这项研究的目的是通过NADPH-心肌黄递酶组织化学和一氧化氮合酶（NOS）免疫组织化学检查自发性高血压大鼠（SHRs）的CB中亚硝化结构的存在和分布，并将其表达模式与年龄进行比较。匹配的血压正常的Wistar大鼠（NWR）。组织化学显示，化学感受器的肾小球细胞为NADPH-d阴性，但周围有细小的阳性静脉曲张，它们也分散在肾小球周围的基质中。NADPH-d反应性纤维在SHR的CB中显示相同的分布模式，但是与NWR相比，它们的染色活性较弱。高血压CB中的肾小球，肾小球内和血管周围的静脉曲张细纤维组成性表达NOS的两种亚型，即nNOS和eNOS，但不包括球蛋白或Sustentacular细胞。另外，SHR的CB中的球状细胞和血管簇对第三种已知的NOS同工酶iNOS表现出中等的免疫反应性。本研究表明，与正常血压对照组相比，在高血压CB中，nNOS和eNOS蛋白表达在统计学上显着下调，而在结冰组织中iNOS表达上调。