:Objective To explore theprotective 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 establishedby exposure to hypoxia (100% N_2) for 90 s and 4 ℃for 10 min, twice a day for 3consecutive days. Rats in group A received smectite powder 0. 6 g/ (kg·d) and thosein group B did not. Rats in groups C and D served as control groups with those in group Dreceived smectite powder 0. 6 g/(kg·d) and those in group C did not. The rats weresacrificed on day 4 and intestines were collected. The apoptosis ratio of intestinal cellswas determined with flow cytometry and the morphological changes in intestinal mucosa wereobserved under light and electron microscopes, and the content of PAF, TNF-a were testedby ELISA. Results The rats in group A and B had diarrhea, abdominal distention, slowgrowth and development, less activity, and the apoptosis cells and apoptic body wereobserved 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 histologicalevaluation 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 thehistopatholigical score and the apoptosis ratio of intestinal cells of group B, those ofgroup A reduced, but remained significantly higher than those of group C and D. In groupA, B, C and D, the contents of PAF in intestinal tissue (expressed as pg/mg prot) were385. 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 reducedsignificantly, while higher than those of group C and D. NEC model and smectiteintervention affected the histopatholigical score, apoptosis ratio of intestinal cells andthe contents of PAF, TNF-α. There was interaction between NEC model and smectiteintervention. Conclusions Smectite may reduce the apoptosis ratio of intestinal cells anddecrease the endogenous production of PAF and TNF-o in intestinal tissue, which eventuallyprotect the intestinal against NEC. Key words: Enterocolitis, necrotizing; Animals,newborn; Rats; Silicates; Apoptosis