Evaluation of the interaction between myogenic response and endothelium-derived factor by a microvessel perfusion system

1.离体犬股动脉：一种NO微电极（直径100 μm）插入血管中，在其中测量流动诱导的内皮源性NO产生，NO产生以约24秒的时间常数变化，并且观察到灌注速率与产生的NO之间的线性关系。灌注NO合成酶（NOS）的辅助因子BH_4可使这种抑制作用消失。同时灌流SNAP和Tiron，超氧化物清除剂没有影响内源性NO的产生。总之，外源性NO灌流引起细胞内BH_4水平下降，导致NOS释放超氧化物，NO与超氧化物反应产生过氧亚硝基阴离子，使NOS活性减弱.离体大鼠肠系膜小动脉：用NO荧光指示剂（NTA-2DA）显示血管壁内NO，在硝酸甘油（NTG）灌注过程中观察到均匀分布的NO荧光。此外，还发现含巯基的分子参与了NTG衍生的NO生成机制.离体灌流大鼠心脏：当灌注压从100 cmH_2O降至50 cmH_2O时，冠状动脉灌注率下降一半，而NO生成量增加近一倍。尽管灌注压降低导致冠状动脉灌注率降低，但NO生成量增加与氧供应调节机制有关。全身NO产生率的估计方法：测量简单禁食14小时后收集的血液样品中的血浆硝酸盐水平，通过单室分析估计全身NO产生率约为600 nmol/min。与尿硝酸盐和RI等其他方法比较，其估计值具有可比性。

1. Isolated canine femoral artery : An NO microelectrode (100 μm in diameter) was inserted into the vascular media where flow-induced endothelium-derived NO production was measured NO production was changed with a time constant of about 24 sec, and a linear relation was observed between perfusion rate and produced NO.Flow-induced NO production was attenuated by exogenous NO (SNAP), and this suppressive effect was disappeared by perfusing BH_4, a cofactor of NO synthase (NOS). Simultaneous perfusion of SNAP and Tiron, superoxide scavenger did not affect endogenous NO production. Collectively, exogenous NO perfusion induces a decrease in intracellular BH_4 level, leading to superoxide release from NOS.Reaction between NO and superoxide is known to produce peroxynitrite, which attenuates NOS activity.2. Isolated rat mesenteric small artery : Intravascular-wall NO was visualized by an NO fluorescent indicator (DAF-2DA), and uniformly distributed NO fluorescence was observed during nitroglycerin (NTG) perfusion. In addition, it was found that thiol-containing molecules are involved in the NTG-derived NO production mechanism.3. Isolated perfused rat heart : When perfusion pressure was decreased from 100 to 50 cmH_2O, coronary perfusion rate decreased by half ; however, NO production was nearly doubled Despite decreased coronary perfusion rate by decreased perfusion pressure, NO production was increased in association with regulation mechanism of oxygen supply.4. Estimation method of systemic NO production rate : Plasma nitrate level in blood samples collected after simple 14-hr fasting was measured, and systemic NO production rate was estimated to be about 600 nmol/min by a single-compartment analysis. Compared with other previous estimation methods such as urinary nitrate and RI, estimated values were comparable.