Tojo A, Gross S S, Zhang L, Tisher C C, Schmidt H H, Wilcox C S, Madsen K M
Division of Nephrology, University of Florida, Gainesville 32610-0224.
J Am Soc Nephrol. 1994 Jan;4(7):1438-47. doi: 10.1681/ASN.V471438.
Nitric oxide (NO) is a messenger molecule that functions as a vasodilator and accounts for the biologic activity of endothelium-derived relaxing factor (EDRF). The enzyme responsible for NO production, NO synthase (NOS), exists in different isoforms. Some are expressed constitutively in various tissues, whereas others require induction by endotoxin and cytokines. There is evidence that NO plays an important role in the regulation of basal renal vascular resistance and in the tubuloglomerular feedback response. Specific antibodies to a constitutive NOS isolated from rat brain (B-NOS) and an inducible NOS isolated from rat aortic smooth muscle (VSM-NOS) were used to establish the cellular and subcellular distribution of NOS in the kidney. Kidneys from normal rats were preserved and processed for light and electron microscopic immunohistochemical studies using both a preembedding and a postembedding horseradish peroxidase technique. By light microscopy, strong immunostaining for B-NOS was observed in the juxtaglomerular apparatus, where it was located in cells of the macula densa. In contrast, immunostaining for VSM-NOS was specifically located in the terminal afferent arteriole and occasionally also in the initial efferent arteriole in the juxtaglomerular apparatus. In addition, faint immunostaining was present in the entire distal tubule. There was no labeling of arcuate or interlobular arteries. The injection of lipopolysaccharide was associated with increased immunostaining for VSM-NOS in the afferent arteriole but had no effect on B-NOS staining. By electron microscopy, B-NOS immunostaining was present throughout the cytoplasm of the macula densa cells, where it appeared to be associated mainly with small vesicles. Immunostaining for VSM-NOS in the afferent arteriole exhibited a patchy distribution in some cells, whereas other cells were stained throughout the cytoplasm. These results indicate that two distinct isoforms of NOS are present in the juxtaglomerular apparatus and support the hypothesis that NOS is involved in the regulation of tubuloglomerular feedback and glomerular capillary pressure.
一氧化氮（NO）是一种信使分子，具有血管舒张功能，是内皮源性舒张因子（EDRF）的生物学活性物质。负责产生NO的酶，即一氧化氮合酶（NOS），以不同的同工型存在。有些在各种组织中组成性表达，而其他的则需要内毒素和细胞因子诱导。有证据表明，NO在基础肾血管阻力调节和肾小管-肾小球反馈反应中起重要作用。使用从大鼠脑部分离的组成型NOS（B-NOS）和从大鼠主动脉平滑肌分离的诱导型NOS（VSM-NOS）的特异性抗体，来确定NOS在肾脏中的细胞和亚细胞分布。对正常大鼠的肾脏进行保存，并使用包埋前和包埋后辣根过氧化物酶技术进行光镜和电镜免疫组织化学研究。光镜下，在肾小球旁器中观察到B-NOS的强免疫染色，其位于致密斑细胞中。相比之下，VSM-NOS的免疫染色特异性地位于终末入球小动脉，偶尔也位于肾小球旁器中的起始出球小动脉。此外，整个远曲小管中存在微弱的免疫染色。弓形动脉或小叶间动脉没有标记。注射脂多糖与入球小动脉中VSM-NOS的免疫染色增加有关，但对B-NOS染色没有影响。电镜下，致密斑细胞的整个细胞质中都有B-NOS免疫染色，并主要与小泡相关。入球小动脉中VSM-NOS的免疫染色在一些细胞中呈斑片状分布，而其他细胞则整个细胞质都被染色。这些结果表明，肾小球旁器中存在两种不同同工型的NOS，并支持NOS参与肾小管-肾小球反馈和肾小球毛细血管压力调节的假说。
