Ujiie K, Yuen J, Hogarth L, Danziger R, Star R A
Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas 75235-8856.
Am J Physiol. 1994 Aug;267(2 Pt 2):F296-302. doi: 10.1152/ajprenal.1994.267.2.F296.
Nitric oxide (NO) has effects on renal blood flow, glomerular filtration rate, renin secretion, and renal sodium excretion. Four isoforms of nitric oxide synthase (NOS) have been cloned to date. However, the molecular identity of NOS present in the renal vasculature is unknown. Endothelial NOS (NOS-III) is regulated both acutely by cell calcium and chronically by shear stress. To determine if renal blood vessels and the glomerulus express NOS-III mRNA, we used degenerate polymerase chain reaction (PCR) to clone a portion of rat NOS-III. We then assayed NOS-III mRNA in microdissected renal structures by reverse transcriptase-PCR. NOS-III mRNA was expressed at high levels in glomeruli, arcuate vessels, and interlobular artery/afferent arterioles. NOS-III mRNA was detected inconsistently in proximal tubules, thick ascending limbs, and cortical and inner medullary collecting ducts. Previous studies have shown that chronic oral treatment with the NOS inhibitor N omega-nitro-L-arginine methyl ester (L-NAME) decreases NO synthesis and causes hypertension. To determine if the systemic blockade occurs only by competitive inhibition, we determined the effect of L-NAME on glomerular NOS-III mRNA. L-NAME administration (5 days) decreased NOS-III mRNA in the glomerulus to 25 +/- 12% of control levels. We conclude that endothelial NOS-III mRNA is preferentially expressed in the glomerulus and renal vasculature, where it can modulate renal blood flow and glomerular filtration rate. Furthermore, glomerular NOS-III may be modulated at the level of mRNA abundance in vivo by systemic L-NAME.(ABSTRACT TRUNCATED AT 250 WORDS)
一氧化氮（NO）对肾血流量、肾小球滤过率、肾素分泌及肾钠排泄均有影响。迄今为止，已克隆出四种一氧化氮合酶（NOS）同工型。然而，肾血管中存在的NOS的分子特性尚不清楚。内皮型NOS（NOS-III）受细胞钙的急性调节和剪切应力的慢性调节。为了确定肾血管和肾小球是否表达NOS-III mRNA，我们使用简并聚合酶链反应（PCR）克隆大鼠NOS-III的一部分。然后，我们通过逆转录酶-PCR检测显微解剖的肾结构中的NOS-III mRNA。NOS-III mRNA在肾小球、弓形血管和小叶间动脉/入球小动脉中高水平表达。在近端小管、髓袢升支粗段以及皮质和髓质内集合管中，NOS-III mRNA的检测结果不一致。先前的研究表明，用NOS抑制剂Nω-硝基-L-精氨酸甲酯（L-NAME）进行慢性口服治疗会降低NO合成并导致高血压。为了确定全身阻断是否仅通过竞争性抑制发生，我们确定了L-NAME对肾小球NOS-III mRNA的影响。给予L-NAME（5天）可使肾小球中的NOS-III mRNA降至对照水平的25±12%。我们得出结论，内皮型NOS-III mRNA在肾小球和肾血管中优先表达，在那里它可以调节肾血流量和肾小球滤过率。此外，全身性L-NAME可能在体内mRNA丰度水平上调节肾小球NOS-III。（摘要截短于250字）
