Hu Zhang-yan, Cheng Shang-mu, Zhu Qing-xian
Department of Anatomy, Medical College of Shaoxing University, Shaoxing 312000, PR China.
Zhonghua Shao Shang Za Zhi. 2006 Dec;22(6):419-22.
To investigate the influence of induced nitric oxide synthase (iNOS) expression on apoptosis of thymocyte in burn rats, and to explore the relationship between NO and pathological lesion of the thymus gland in burn rats.
Fifty-six male Wistar rats were enrolled in the study and randomized into control( C, n = 8,without treatment) , burn ( B, n = 24) , and S-methylisothiourea( SMT, n = 24) groups. Equal amount of isotonic saline solution and SMT(7. 5 mg/kg) were respectively intravenously infused into the rats in B and SMT groups after being inflicted with 30% TBSA full-thickness burns. The weight of thymus gland in each group were weighed, and thymocyte apoptosis and iNOS expression were determined with TUNEL method and immunohistochemistry, respectively at 6,24,72 postburn hours( PBH) , with 8 rats at each time-point. The number of apoptotic cells and the density of iNOS positive cells in thymus was measured by stereological method.
The weight of thymus in B group at 24 and 72 PBH [ (153+/- 14) , (91+/-22) mg] were obviously heavier than those in C group, but much lighter than those in SMT group ( P < 0.01). A few apoptotic cells and iNOS positive cells were observed in cortex and medulla of thymus in C group, while they were observed in B group at 6 PBH, and the number of cells began to increase at 24 PBH, distributing in medulla,parenchyma, the boundary of cortex, and medulla under capsule. The iNOS positive cells in B group at 24 PBH were distributed around the interlobular septum. A large number of cortical cells with brown staining were observed in B group at 72 PBH, and the number of iNOS positive cells also increased, with scattered distribution and clear cell boundary. Fewer positive cells with uneven distribution, no iNOS positive cells, and few apoptotic foci were observed in SMT group after burns. The density of apoptotic cells in B group at 24 and 72 PBH was (2. 428 +/-0. 728) x 10(-5)/microm(3) and (5. 586 +/- 1.233) x 10(-5)/microm(3), respectively, which was obviously higher than that in C and SMT group. The density of iNOS positive cells in B group was increased in a time-dependent manner( P <0. 05).
The apoptotic rate of thymocyte in severely burn rats increases early after burns. The up-regulation of iNOS expression in thymus can promote apoptosis of thymocytes, while SMT can partially ameliorate this phenomenon.
探讨诱导型一氧化氮合酶（iNOS）表达对烧伤大鼠胸腺细胞凋亡的影响，以及一氧化氮（NO）与烧伤大鼠胸腺病理损害的关系。
选取56只雄性Wistar大鼠，随机分为对照组（C组，n = 8，未处理）、烧伤组（B组，n = 24）和S-甲基异硫脲（SMT）组（n = 24）。B组和SMT组大鼠在造成30%体表面积全层烧伤后，分别静脉输注等量的生理盐水和SMT（7.5 mg/kg）。分别于伤后6、24、72小时（PBH）每组取8只大鼠，称取各组大鼠胸腺重量，采用TUNEL法和免疫组化法分别检测胸腺细胞凋亡及iNOS表达。用体视学方法测量胸腺中凋亡细胞数和iNOS阳性细胞密度。
B组伤后24、72小时PBH时胸腺重量[（153±14），（91±22）mg]明显重于C组，但明显轻于SMT组（P < 0.01）。C组胸腺皮质和髓质可见少量凋亡细胞和iNOS阳性细胞，B组伤后6小时PBH可见凋亡细胞和iNOS阳性细胞，24小时PBH时细胞数量开始增加，分布于髓质、实质、皮质与髓质交界处及被膜下。B组伤后24小时PBH时iNOS阳性细胞分布于小叶间隔周围。B组伤后72小时PBH可见大量皮质细胞呈棕色染色，iNOS阳性细胞数量也增加，呈散在分布，细胞边界清晰。SMT组烧伤后阳性细胞较少，分布不均，未见iNOS阳性细胞，凋亡灶较少。B组伤后24、72小时PBH时凋亡细胞密度分别为（2.428±0.728）×10⁻⁵/μm³和（5.586±1.233）×10⁻⁵/μm³，明显高于C组和SMT组。B组iNOS阳性细胞密度呈时间依赖性增加（P < 0.05）。
重度烧伤大鼠伤后早期胸腺细胞凋亡率增加。胸腺中iNOS表达上调可促进胸腺细胞凋亡，而SMT可部分改善此现象。
