Brovkovych V, Dobrucki L W, Brovkovych S, Dobrucki I, Kalinowski L, Kiechle F, Malinski T
Department of Chemistry and Biochemistry, Ohio University, Athens, OH 45701, USA.
Clin Chem. 2001 Jun;47(6):1068-74.
Excessive continuous NO release from inducible NO synthase over prolonged periods under pathological conditions, such as endotoxemia, contributes significantly to circulatory failure, hypotension, and septic shock. This NO production during endotoxemia is accompanied by superoxide release, which contributes to the fast decay of NO. Therefore, the amount of NO that diffuses to target sites may be much lower than the total amount released under pathological conditions.
We performed in vivo and ex vivo measurements of NO (electrochemical) and ex vivo in situ measurements of superoxide, peroxynitrite (chemiluminescence), and nitrite and nitrate (ultraviolet-visible spectroscopy). We determined the effect of lipopolysaccharide administration (20 mg/kg) on diffusible NO, total NO (diffusible plus consumed in chemical reactions), and superoxide and peroxynitrite release in the pulmonary arteries of rats.
An increase in diffusible NO generated by constitutive NO synthase was observed immediately after administration of lipopolysaccharide, reaching a plateau (145 +/- 18 nmol/L) after 540 +/- 25 s. The plateau was followed by a decrease in NO concentration and its subsequent gradual increase after 45 min because of NO production by inducible NO synthase. The concentration of superoxide increased from 16 +/- 2 nmol/L to 30 +/- 3 nmol/L after 1 h and reached a plateau of 41 +/- 4 nmol/L after 6 h. In contrast to the periodic changes in the concentration of diffusible NO, the total concentration of NO measured as a sum of nitrite and nitrate increased steadily during the entire period of endotoxemia, from 2.8 +/- 0.2 micromol/L to 10 +/- 1.8 micromol/L.
The direct measurement of NO concentrations in the rat pulmonary artery demonstrates dynamic changes throughout endotoxemia, which are related to the production of superoxide and the subsequent increase in peroxynitrite. Monitoring endotoxemia with total nitrate plus nitrite is not sensitive to these fluctuations in NO concentration.
在病理状态下，如内毒素血症，诱导型一氧化氮合酶长时间过度持续释放一氧化氮，对循环衰竭、低血压和感染性休克有显著影响。内毒素血症期间一氧化氮的产生伴随着超氧化物的释放，这导致一氧化氮快速衰减。因此，扩散到靶位点的一氧化氮量可能远低于病理条件下释放的总量。
我们进行了体内和体外一氧化氮测量（电化学法），以及超氧化物、过氧亚硝酸盐（化学发光法）和亚硝酸盐与硝酸盐（紫外可见光谱法）的体外原位测量。我们测定了脂多糖给药（20mg/kg）对大鼠肺动脉中可扩散一氧化氮、总一氧化氮（可扩散的加上化学反应中消耗的）以及超氧化物和过氧亚硝酸盐释放的影响。
脂多糖给药后立即观察到组成型一氧化氮合酶产生的可扩散一氧化氮增加，540±25秒后达到平台期（145±18nmol/L）。平台期后一氧化氮浓度下降，45分钟后由于诱导型一氧化氮合酶产生一氧化氮，其浓度随后逐渐增加。超氧化物浓度在1小时后从16±2nmol/L增加到30±3nmol/L，6小时后达到41±4nmol/L的平台期。与可扩散一氧化氮浓度的周期性变化相反，以内硝酸盐和硝酸盐总和测量的一氧化氮总浓度在内毒素血症的整个期间稳步增加，从2.8±0.2μmol/L增加到10±1.8μmol/L。
大鼠肺动脉中一氧化氮浓度的直接测量表明，在内毒素血症期间存在动态变化，这与超氧化物的产生以及随后过氧亚硝酸盐的增加有关。用总硝酸盐加亚硝酸盐监测内毒素血症对一氧化氮浓度的这些波动不敏感。
