Rachmilewitz D, Karmeli F, Okon E, Bursztyn M
Department of Medicine, Hadassah University Hospital, Mount Scopus, Hebrew University Hadassah Medical School, Jerusalem, Israel.
Gut. 1995 Aug;37(2):247-55. doi: 10.1136/gut.37.2.247.
Enhanced nitric oxide (NO) generation by stimulated NO synthase (NOS) activity may, through its oxidative metabolism contribute to tissue injury in experimental colitis. In this study the possible amelioration of experimental colitis by NG-nitro-L-arginine methyl ester (L-NAME), an inhibitor of NOS activity, was evaluated. Colitis was induced in rats by intracolonic administration of 30 mg trinitrobenzene sulphonic acid (TNB) dissolved in 0.25 ml 50% ethanol or by flushing the colon of capsaicin pretreated rats with 2 ml of 5% acetic acid. In several experiments, L-NAME 0.1 mg/ml was added to the drinking water at the time of colitis induction with TNB or seven days before acetic acid treatment. Rats were killed at various time intervals after induction of colitis. A 10 cm distal colonic segment was isolated, weighed, lesion area measured, and explants organ cultured for 24 hours for determination of NO generation by the Greiss reaction. The rest of the mucosa was scraped for determination of myeloperoxidase and NOS activities and leukotriene generation. In TNB treated rats mean arterial pressure was also determined up to 72 hours after damage induction, with or without cotreatment with nitroprusside. L-NAME significantly decreased the extent of tissue injury in TNB treated rats. Seven days after TNB treatment lesion area was reduced by 55%, colonic weight by 37%, and myeloperoxidase and NOS activity by 59% and 42%, respectively. Acetic acid induced colitis in capsaicin pretreated rats was also significantly decreased by L-NAME. Twenty four hours after acetic acid treatment lesion area was reduced by 61%, colonic weight by 21% and NOS activity by 39%. Mean (SEM) arterial blood pressure in TNB+L-NAME treated rats was 37.6 (8.1) mm Hg higher than in TNB treated rats, an effect that was only partially abolished by nitroprusside. These results show that inhibition of NO synthesis by an L-arginine analogue significantly ameliorates the extent of tissue injury in two models of experimental colitis, an effect that is not due only to its vasoconstrictor properties. Modulation of NO generation may be a novel therapeutic approach in inflammatory bowel disease.
受刺激的一氧化氮合酶（NOS）活性增强所产生的一氧化氮（NO），可能通过其氧化代谢作用导致实验性结肠炎中的组织损伤。在本研究中，评估了NOS活性抑制剂NG-硝基-L-精氨酸甲酯（L-NAME）对实验性结肠炎的可能改善作用。通过向大鼠结肠内注射溶解于0.25 ml 50%乙醇中的30 mg三硝基苯磺酸（TNB），或用2 ml 5%乙酸冲洗辣椒素预处理大鼠的结肠来诱导结肠炎。在一些实验中，在以TNB诱导结肠炎时或在乙酸处理前七天，将0.1 mg/ml的L-NAME添加到饮用水中。在诱导结肠炎后的不同时间间隔处死大鼠。分离出10 cm远侧结肠段，称重，测量损伤面积，并将外植体进行器官培养24小时，通过格里斯反应测定NO的生成量。刮取其余黏膜用于测定髓过氧化物酶和NOS活性以及白三烯的生成量。在TNB处理的大鼠中，还在损伤诱导后72小时内测定平均动脉压，无论是否与硝普钠联合治疗。L-NAME显著降低了TNB处理大鼠的组织损伤程度。TNB处理七天后，损伤面积减少了55%，结肠重量减少了37%，髓过氧化物酶和NOS活性分别减少了59%和42%。L-NAME也显著减轻了辣椒素预处理大鼠中乙酸诱导的结肠炎。乙酸处理24小时后，损伤面积减少了61%，结肠重量减少了21%，NOS活性减少了39%。TNB + L-NAME处理的大鼠的平均（SEM）动脉血压比TNB处理的大鼠高37.6（8.1）mmHg，硝普钠仅部分消除了这一效应。这些结果表明，L-精氨酸类似物抑制NO合成可显著减轻两种实验性结肠炎模型中的组织损伤程度，这一效应并非仅归因于其血管收缩特性。调节NO生成可能是炎症性肠病的一种新的治疗方法。
