ACh dilates pial arterioles in endothelial and neuronal NOS knockout mice by NO-dependent mechanisms.
ACh dilates pial arterioles in endothelial and neuronal NOS knockout mice by NO-dependent mechanisms.
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ACh 通过 NO 依赖性机制扩张内皮和神经元 NOS 敲除小鼠的软脑膜小动脉。
DOI：
10.1152/ajpheart.1996.271.3.h1145
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发表时间：
1996
期刊：
影响因子：
--
通讯作者：
Moskowitz,MA
中科院分区：
文献类型：
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作者：
Meng,W;Ma,J;Ayata,C;Hara,H;Huang,PL;Fishman,MC;Moskowitz,MA
我们使用内皮一氧化氮合酶 (eNOS) 或神经元 NOS (nNOS) 基因缺失的小鼠来研究 eNOS 和 nNOS 在乙酰胆碱 (ACh) 诱导的软脑膜小动脉（20-30 微米）松弛中的作用。通过闭合颅窗通过活体显微镜测量软脑膜小动脉直径，并通过下皮层中[3H]精氨酸到[3H]瓜氨酸的转化来测定NOS活性。 ACh 灌注（1、10 µM）在所有三种小鼠品系中均引起阿托品敏感的剂量依赖性小动脉扩张。在 10 microM 剂量下，野生型 (n = 25)、nNOS 突变体 (n = 15) 和 eNOS 突变体 (n = 20) 小鼠中分别记录到 20 +/- 2、31 +/- 3 和 23 +/- 3% 的增加。 NG-硝基-L-精氨酸（L-NNA，1 mM）灌注可抑制皮质 NOS 活性 > 70%，并消除野生型小鼠中的反应，同时阻止 eNOS 突变型和 nNOS 突变型小鼠中约 50% 的扩张。仅在 eNOS 突变体中，河豚毒素 (TTX) 灌注 (1 µM) 会减弱 ACh 诱导的扩张 (n = 6)。 eNOS 突变小鼠中 L-NNA 后的残余扩张可以被 TTX 加 L-NNA 完全阻断。我们的研究结果表明，1）ACh 通过 NOS 依赖性机制扩张野生型小鼠的软膜小动脉，2）nNOS 突变小鼠的反应类似于野生型反应，除了对 ACh 的扩张增强和 L-NNA 敏感性降低之外，3）令人惊讶的是，eNOS 突变小鼠的反应部分依赖于 NOS，并被 TTX 和 L-NNA 减弱。由于 nNOS 在 eNOS 突变体中组成型表达，因此这些发现与 TTX 结果相结合表明，nNOS 依赖性机制可以补偿靶向基因破坏后 eNOS 活性的慢性丧失。
We used mice with deletions in either the endothelial nitric oxide synthase (eNOS) or neuronal NOS (nNOS) gene to investigate the role of eNOS and nNOS in acetylcholine (ACh)-induced relaxation of pial arterioles (20-30 microns). Pial arteriolar diameter was measured by intravital microscopy through a closed cranial window, and NOS activity was determined by the conversion of [3H]arginine to [3H]citrulline in subjacent cortex. ACh superfusion (1, 10 microM) caused atropine-sensitive dose-dependent arteriolar dilation in all three mouse strains. At 10 microM, increases of 20 +/- 2, 31 +/- 3, and 23 +/- 3% were recorded in wild-type (n = 25), nNOS mutant (n = 15), and eNOS mutant (n = 20) mice, respectively. NG-nitro-L-arginine (L-NNA, 1 mM) superfusion inhibited cortical NOS activity by > 70% and abrogated the response in wild-type mice while blocking the dilation by approximately 50% in eNOS mutant and nNOS mutant mice. Only in the eNOS mutant did tetrodotoxin (TTX) superfusion (1 microM) attenuate ACh-induced dilation (n = 6). The residual dilation after L-NNA in eNOS mutant mice could be blocked completely by TTX-plus L-NNA. Our findings indicate that 1) ACh dilates pial arterioles of wild-type mice by NOS-dependent mechanisms as reported in other species, 2) the response in nNOS mutant mice resembles the wild-type response except for enhanced dilation to ACh and reduced L-NNA sensitivity, and 3) surprisingly, the response in eNOS mutant mice is partially NOS dependent and attenuated by both TTX and L-NNA. Because nNOS is constitutively expressed in eNOS mutants, these findings coupled with the TTX results suggest that an nNOS-dependent mechanism may compensate for the chronic loss of eNOS activity after targeted gene disruption.