预防性应用天然蒙脱石对新生大鼠坏死性小肠结肠炎肠损伤的保护作用

目的 探讨预防性应用天然蒙脱石对新生大鼠坏死性小肠结肠炎(necrotizing entero-colitis,NEC)模型肠损伤的保护作用及可能机制. 方法 按析因设计,32只新生SD大鼠随机分成4组,每组8只.A组为NEC模型,出生48 h起给予天然蒙脱石0.6 gl(kg·d)灌胃;B组为NEC模型,未添加天然蒙脱石;C组为对照,未添加天然蒙脱石;D组为对照,出生48 h起给予天然蒙脱石0.6 g/(kg·d)灌胃.SD新生大鼠出生后48 h开始采用鼠配方奶喂养,100%氮气90 s,4℃10 min,每天2次,连续3 d,建立新生大鼠NEC模型.A、B组在造模结束后24 h和C、D组新生大鼠空腹断头处死,留取十二指肠下端至直肠上端肠管进行肠细胞凋亡率检测(流式细胞仪)、电镜观察和血小板活化因子(platelet-actvating factor,PAF)、肿瘤坏死因子-α(tumor necrosis factor-α,TNF-α)含量(ELISA 法)检测.所有新生大鼠均留取回盲部近端肠管进行肠组织损伤评分. 结果造模后,A、B组新生鼠相继出现腹泻、腹胀、萎靡、活动减少,生长减慢;透射电镜显示肠黏膜出现大量凋亡细胞,形成凋亡小体,A组程度较轻.A、B、C和D组肠组织损伤评分分别为1.42±0.36、3.54±0.50、0.13±0.17和0.17±0.18,肠细胞凋亡率为(11.6±4.6)%、(27.6±9.9)%、(4.8±2.9)%和(3.6±3.8)%,与B组相比,A组肠组织损伤评分和肠细胞凋亡率明显降低,但仍高于C、D两组(P均<0.01).A、B、C和D组肠组织PAF含量(单位为pg/mg prot)分别为385.0 4-308.0.1663.24-576.1、40.8±40.4和37.1±33.1,TNF-α含量(单位为pg/mg prot)为46.4±15.1、258.1±281.7、13.2±12.2和12.44-8.8.B组肠组织PAF、TNF-α含量明显高于C、D组;与B组相比,A组肠组织PAF、TNF-α含量明显降低(P均<0.01).肠组织损伤评分、肠细胞凋亡率及肠组织PAF、TNF-α含量均受造模和预防性应用天然蒙脱石两因素影响,造模与预防性应用天然蒙脱石之间存在交互作用. 结论 预防性应用天然蒙脱石可能通过减少肠细胞凋亡率,降低肠组织PAF、TNF-α含量,从而减轻肠损伤程度.

Protective effect of smectite powder on necrotizing enterocolitis in neonatal rat model

Objective To explore the protective effects and the mechanism of smectite powder in necrotizing enterocolitis(NEC) model of neonatal SD rat. Methods Thirty-two neonatal SD rats were divided into 4 groups (A, B. C and D, 8 rats in each group). Rats in group A and B were NEC models established by exposure to hypoxia (100% N_2) for 90 s and 4 ℃for 10 min, twice a day for 3 consecutive days. Rats in group A received smectite powder 0. 6 g/ (kg·d) and those in group B did not. Rats in groups C and D served as control groups with those in group D received smectite powder 0. 6 g/(kg·d) and those in group C did not. The rats were sacrificed on day 4 and intestines were collected. The apoptosis ratio of intestinal cells was determined with flow cytometry and the morphological changes in intestinal mucosa were observed under light and electron microscopes, and the content of PAF, TNF-a were tested by ELISA. Results The rats in group A and B had diarrhea, abdominal distention, slow growth and development, less activity, and the apoptosis cells and apoptic body were observed in their intestine mucosa. As compared with group B, after given smectite powder, symptoms in the rats of group A were remarkably relieved. The scores of histological evaluation in group A, B, C and D were 1. 42±0. 36, 3. 54±0. 50, 0. 13±0. 17 and 0. 17 ±0.18, respectively, and the apoptosis ratios of intestinal cells were (11. 6 ±4. 6)%, (27. 6 ±9.9)%, (4.8±2.9)% and (3.6±3.8)%, respectively. Compared with the histopatholigical score and the apoptosis ratio of intestinal cells of group B, those of group A reduced, but remained significantly higher than those of group C and D. In group A, B, C and D, the contents of PAF in intestinal tissue (expressed as pg/mg prot) were 385. 0±308. 0, 1663. 2 ±576. 1, 40. 8 ±40. 4 and 37. 1±33.1, and TNF-α (expressed as pg/mg prot) were 46.4±15. 1, 258. 1 ±281. 7, 13. 2±12. 2 and 12. 4±8. 8, respectively. Compared with group B, those in group A reduced significantly, while higher than those of group C and D. NEC model and smectite intervention affected the histopatholigical score, apoptosis ratio of intestinal cells and the contents of PAF, TNF-α. There was interaction between NEC model and smectite intervention. Conclusions Smectite may reduce the apoptosis ratio of intestinal cells and decrease the endogenous production of PAF and TNF-o in intestinal tissue, which eventually protect the intestinal against NEC.