Lee D H, Lee S H, Kwon N S, Kim J C
Department of Ophthalmology, College of Medicine, Chung Ang University, Seoul, Korea.
Invest Ophthalmol Vis Sci. 1997 Apr;38(5):995-1002.
To find the role of nitric oxide (NO) in streptozocin-induced corneal toxicity in rats.
Sprague-Dawley rats were injected intraperitoneally with streptozotocin (65 mg/kg). For exposure to light, each rat cage was placed in a box surrounded with aluminum foil and illuminated for 6 hours per day with two 20-W fluorescent lamps at a distance of 50 cm. When not exposed to light, each cage was placed in a dark room. Some animals with and without light exposure also were treated with and without streptozotocin treatment. Control animals did not receive streptozotocin and were housed in a dark room 24 hours a day. Each group contained 15 rats. After 1, 3, 7, and 10 days of light exposure, concentrations of nitrite and nitrate, stable oxidation products of NO, were measured in the aqueous humor. Corneal changes also were examined by electron microscopy after 10 days. To examine specific NO-induced histopathologic changes, several rats were injected subconjunctivally with a balanced saline solution containing the NO-generating agent (S-nitroso-N-acetyl-D,L-penicillamine or (Z)-I-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1, 2-diolate]).
Concentrations of nitrite and nitrate were highest in the streptozocin-injected rats irradiated while under the fluorescent lamp. On the 10th day of the streptozotocin injection, the concentrations of nitrite and nitrate in streptozocin-treated rats irradiated while under the fluorescent lamp was almost two-and-a-half times greater than that of nontreated rats reared in the dark (111.37 +/- 7.47 microM, 45.43 +/- 3.91 microM, respectively). Slit-lamp biomicroscopy showed that the corneas swelled gradually and opacified by the third day in the irradiated streptozocin-injected group. The corneas became hazy to the point of indistinguishable detail structures by the 10th day, although those of the other rats were relatively clear at the same time. Histopathologically, ultrastructural changes included the remarkable swelling of intracytoplasmic organelles, including mitochondria, and denaturation of collagen fibril was shown in the streptozocin-injected-irradiated rats by the 10th day. The corneas injected with two NO-generating agents, S-nitroso-N-acetyl-D,L-penicillamine and (Z)-1-[2-(2-aminoethyl)-N-(2-ammonioethyl)amino]diazen-1- ium-1, 2-diolate, showed similar but more severe changes.
Nitric oxide can cause damage to the mitochondria, the most important energy source of the cell, and induce ultrastructural damage to the corneal endothelium and fibroblast. The authors suggest that NO is associated with the development of corneal cytotoxicity and that NO production and subsequent cytotoxicity can be prevented by blocking to photoactivation.
探讨一氧化氮（NO）在链脲佐菌素诱导的大鼠角膜毒性中的作用。
将链脲佐菌素（65mg/kg）腹腔注射到Sprague-Dawley大鼠体内。为了使其暴露于光照下，将每个大鼠笼置于用铝箔包围的盒子中，并用两个20W荧光灯每天照射6小时，灯距为50cm。不暴露于光照时，将每个笼子置于暗室中。一些暴露或未暴露于光照的动物也接受或未接受链脲佐菌素治疗。对照动物不接受链脲佐菌素，每天24小时饲养在暗室中。每组包含15只大鼠。在光照暴露1、3、7和10天后，测量房水中亚硝酸盐和硝酸盐（NO的稳定氧化产物）的浓度。10天后通过电子显微镜检查角膜变化。为了检查特定的NO诱导的组织病理学变化，几只大鼠结膜下注射含有NO生成剂（S-亚硝基-N-乙酰-D,L-青霉胺或（Z）-1-[2-（2-氨基乙基）-N-（2-氨乙基）氨基]重氮-1,2-二醇盐）的平衡盐溶液。
在荧光灯下照射的注射链脲佐菌素的大鼠中，亚硝酸盐和硝酸盐的浓度最高。在注射链脲佐菌素的第10天，在荧光灯下照射的链脲佐菌素治疗的大鼠中亚硝酸盐和硝酸盐的浓度几乎是在黑暗中饲养的未治疗大鼠的浓度的两倍半（分别为111.37±7.47μM，45.43±3.91μM）。裂隙灯生物显微镜检查显示，在照射的注射链脲佐菌素的组中，角膜在第3天逐渐肿胀并变得混浊。到第10天，角膜变得模糊不清，细节结构难以分辨，而与此同时其他大鼠的角膜相对清晰。组织病理学上，超微结构变化包括细胞质细胞器（包括线粒体）明显肿胀，到第10天，在注射链脲佐菌素并照射的大鼠中显示胶原纤维变性。注射两种NO生成剂S-亚硝基-N-乙酰-D,L-青霉胺和（Z）-1-[2-（2-氨基乙基）-N-（2-氨乙基）氨基]重氮-1,2-二醇盐的角膜显示出相似但更严重的变化。
一氧化氮可导致对细胞最重要的能量来源线粒体的损伤，并诱导角膜内皮细胞和成纤维细胞的超微结构损伤。作者认为NO与角膜细胞毒性的发展有关，并且通过阻断光激活可以预防NO的产生和随后的细胞毒性。
