Farghali H, Hynie S, Vohnikova Z, Masek K
Institute of Pharmacology, First Faculty of Medicine, Charles University, Prague, Czech Republic.
Int J Immunopharmacol. 1997 Sep-Oct;19(9-10):599-605. doi: 10.1016/s0192-0561(97)00048-9.
Nitric oxide (NO) is a multifunctional messenger in many vertebrates. In the liver, NO was found to play an important but controversial role in injury produced by toxins or sepsis. The purpose of the present investigation was to further characterize the role of NO in hepatocyte oxidative injury. A cellular system formed of immobilized and perfused rat hepatocytes was used to test the ability of the latter to produce endogenous NO after lipopolysaccharide administration in vivo (LPS, 20 mg/kg i.p.) and how hepatocyte functionality competence is modified according to NO level. This cellular system also was used to delineate a relationship between exogenously delivered NO to the perfusion medium as produced by the NO donor, sodium nitroprusside (2.0 and 0.2 mM), and any alteration in the degree of injury as evoked by anoxia/reoxygenation or cumene hydroperoxide (1.0 mM and 0.2 mM). Rat hepatocytes were immobilized in low-gelling agarose and perfused with Williams E medium. Endogenous or exogenous NO was evaluated by measuring the end products of NO (NO2- + NO3-) in the perfusion medium. Functional integrity of hepatocytes was evaluated from lactate dehydrogenase (LD) leakage, urea synthesis in the perfusion medium and lipid peroxides (LP) formation. Normal, anoxia/reoxygenation or cumene hydroperoxide injured hepatocytes did not exhibit measurable NO while LPS-treated hepatocytes produced NO. Apparently, within the present experimental conditions, it seems that there was an inverse relation between the rate of NO produced after LPS administration and the rate of lipid peroxides formed in the hepatocytes. Low concentration of sodium nitroprusside (as NO donor) significantly decreased LD leakage, increased the rate of urea synthesis and increased trypan blue exclusion by hepatocytes in anoxia/reoxygenation or cumene hydroperoxide injured (0.2 mM) cells. Lipid peroxides were decreased by NO in cumene hydroperoxide injured hepatocytes. The present data suggest that NO endogenously produced, or exogenously delivered, has an ameliorative role in mild oxidative liver injury models, but not in severe cases and that inside hepatocytes, there is a very delicate balance between the rate of NO production and its consumption. The disturbance in this balance may be responsible for injury due to the formation of more toxic oxygen species.
一氧化氮（NO）是许多脊椎动物体内的多功能信使。在肝脏中，已发现NO在毒素或败血症所致损伤中发挥重要但存在争议的作用。本研究的目的是进一步明确NO在肝细胞氧化损伤中的作用。采用由固定化和灌注大鼠肝细胞组成的细胞系统，来测试体内给予脂多糖（LPS，20mg/kg腹腔注射）后肝细胞产生内源性NO的能力，以及肝细胞功能能力如何根据NO水平而改变。该细胞系统还用于描绘由NO供体硝普钠（2.0和0.2mM）产生的外源性NO释放到灌注培养基中与缺氧/复氧或氢过氧化异丙苯（1.0mM和0.2mM）所引发的损伤程度变化之间的关系。将大鼠肝细胞固定在低熔点琼脂糖中，并用Williams E培养基灌注。通过测量灌注培养基中NO的终产物（NO2- + NO3-）来评估内源性或外源性NO。从乳酸脱氢酶（LD）泄漏、灌注培养基中的尿素合成以及脂质过氧化物（LP）形成来评估肝细胞的功能完整性。正常、缺氧/复氧或氢过氧化异丙苯损伤的肝细胞未表现出可测量的NO，而LPS处理的肝细胞产生了NO。显然，在本实验条件下，LPS给药后产生的NO速率与肝细胞中形成的脂质过氧化物速率之间似乎存在反比关系。低浓度的硝普钠（作为NO供体）显著降低了缺氧/复氧或氢过氧化异丙苯损伤（0.2mM）细胞中的LD泄漏，提高了尿素合成速率，并增加了肝细胞对台盼蓝的排斥率。在氢过氧化异丙苯损伤的肝细胞中，NO降低了脂质过氧化物。目前的数据表明，内源性产生或外源性给予的NO在轻度氧化肝损伤模型中具有改善作用，但在严重情况下则不然，并且在肝细胞内，NO产生速率与其消耗之间存在非常微妙的平衡。这种平衡的紊乱可能是由于形成更多毒性氧物种而导致损伤的原因。
