N-甲基-N-亚硝脲对大鼠光感受器细胞毒性作用的形态学改变

目的:观察N-甲基-N-亚硝脲(N—methyl—N—nitrosourea，MNU)对SD大鼠光感受器细胞毒性作用的形态学改变。方法：雌性SD大鼠76只，分12组，正常对照组4只，其余组各6只。于大鼠生后50d，分别一次腹腔注射MNU 40mg／kg、60mg／kg和80mg／kg。在MNU处理后24h、48h、3d和7d，处死大鼠，取眼球，做组织学检查。结果：不同剂量的MNU均引起视网膜损伤，其损伤的程度与MNU剂量呈正比。作用24h后，可见不同程度的视网膜光感受器细胞核固缩和光感受器细胞外节部定向障碍；48h或3d后，可见光感受器细胞丧失；7d后，外颗粒层和光感受层仅剩下少数几层或几乎完全消失。结论：MNU对大鼠视网膜光感受器细胞有选择性的毒性作用，该作用呈剂量和时间依赖性。

The Toxic Effect of N-methyl-N- nitrosourea on the Morphological Changes of Photoreceptors in Rats

Objective To observe the toxic effect of N-methyl-N-nitrosourea (MNU) on the morphological changes of photoreceptors in rats. Methods 76 50-day old female rats were divided into 3 experimental groups (24 per group) and one control group (4 per group). Each experimental group received a single intraperitoneal injection of MNU of 40mg/kg, 60mg/kg or 80mg/kg body weight. At 24h, 48 h, 3d and 7d after the administration of MNU, 6 rats from each group were sacrificed and both eyes were enucleated immediately and processed for histological examination. Results It was found that all doses of MNU could damage the retina. The first evidence of diverse retinapathy at 24 h after the application of MNU was pyknosis of photoreceptor cell nuclei and the disorientation of the photoreceptor outer segments. At 48h and 3d post treatment there were significant loss of photoreceptor cells. The outer nuclear layers and photoreceptor layers were reduced to only a few layers of cells or almost completely lost at 7d. Conclusion The results demonstrated that MNU could selectively damage the photoreceptor cells in the retina of the rats, which was dose and time- dependent.