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

1. 离体犬股动脉：将直径为100 μm的NO微电极插入血管介质中，测量血管中血流诱导的内皮源性NO的产生，在24秒左右的时间常数内，NO的产生发生变化，灌注速率与产生的NO呈线性关系。外源NO （SNAP）可减弱血流诱导的NO生成，而注入NO合成酶（NOS）辅助因子BH_4后，这种抑制作用消失。同时灌注SNAP和铁、超氧化物清除剂不影响内源性NO的产生。总的来说，外源性NO灌注诱导细胞内BH_4水平降低，导致NOS释放超氧化物，已知NO与超氧化物反应产生过氧亚硝酸盐，降低NOS活性。离体大鼠肠系膜小动脉：用NO荧光指示剂（DAF-2DA）显示血管壁NO，硝酸甘油（NTG）灌注时观察到均匀分布的NO荧光。此外，还发现含硫醇分子参与了ntg衍生的NO生成机制。离体灌注大鼠心脏：当灌注压从100 cmH_2O降至50 cmH_2O时，冠状动脉灌注率降低一半；尽管灌注压降低降低了冠状动脉灌注率，但一氧化氮的产生与供氧调节机制有关。全身NO生成速率估算方法：测定单纯禁食14小时后采集的血液中血浆硝酸盐水平，单室分析估计全身NO生成速率约为600 nmol/min。与其他先前的估计方法如尿硝酸盐和RI相比，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.