| Objective To explore the protective effects and the mechanism of smectite powder in inhibit intestinal injury of neonatal Sprague-Dewley rat necrotizing enterocolitis(NEC) model.Methods According to 2×2 factor analysis, 32 neonate Sprague-Dewley rats(48 hours olds, weighing 5～10g) were divided into 4 groups(A, B, C and D, n=8 rats each groups). Rats in Group A and B were made into NEC models as follows: separate from mother rats and feeding with rat milk substitute, hypoxia(100%N2) for 90 second and 4℃cold exposure for 10 minutes, twice a day during 3 consecutive days. Rats in group A was given smectite powder(0.6g/kg/d) and rats in group B was not. Rats in groups C and D served as control groups, as well as rats in group D was given smectite powder(0.6g/kg/d) and those in group C was not. On the 4th day the rats were sacrificed and intestinal tissue were collected. The apoptosis ratio of intestinal cells were determined with flow cytometry(FCM) and the morphological changes in intestinal musca were observed under light and electron microscope. Another 32 neonate Sprague-Dewley rats were divided into 4 groups also, and the empirical methods were same as described above. The intestinal tissue were obtained to measure the content of PAF, TNF-αwith ELISA(pg/mg prot). The intestine around ileocecal junction of all the subjects were scored in double-blind way, and the mean score more than 2 were considered NEC. Kruskal-Wallis H test, factorial ANOVA were used to analyze difference among various groups.α=0.05 was considered significant.Result [1]After separate from mother rats, feeding with rat milk substitute and induced by hypoxia and cold exposure several continual times, neonatal rats in Groups A and B had diarrhea, abdominal distention, growth and development stepping down, activity reducing, and the apoptosis cells and apoptic body in intestine mucosa was observed in some degree. As compared with group B, there were remarkably relieved after given smectite powder in group A. The scores of histological evaluation(?x±s ) 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, and the apoptosis ratio of intestinal cells were 11.6±4.6, 27.6±9.9, 4.8±2.9 and 3.6±3.8, respectively. The score of histopatholigical and the apoptosis ratio of intestinal cells had significant difference among groups. Comparing with that of group B, the score of histopatholigical and the apoptosis ratio of intestinal cells of group A reduced, but that of group A was higher than two control groups significantly. [3]In Group A, B, C and D, the content of PAF(?x±s, pg/mg prot ) in intestinal tissue were 385.0±308.0, 1663.2±576.1, 40.8±40.4 and 37.1±33.1, and the TNF-αwere 46.4±15.1, 258.1±281.7, 13.2±12.2 and 12.4±8.8, respectively. There were significant difference about PAF, TNF-αamong groups. Comparing with those in group B, the contents of PAF, TNF-αin group A reduced significantly, but they were higher thangroup C and D, and differences were significant. [3]By factorial ANOVA, two factors of model and smectite powder intervention had taken effect on the score of histopatholigical, the apoptosis ratio of intestinal cells and the contents of PAF, TNF-α. There were interaction between model and smectite powder intervention. By spearman correlation analysis, the relation of the apoptosis ratio of intestinal cells, the contents of PAF, TNF-αin intestinal tissue and the degree of intestinal injury were positive(rapoptosis ratio=0.853, rPAF=0.852, rTNF-α=0.839, p<0.01).Conclusion Smectite powder is beneficial to reduce the intestinal injury of neonate rats caused by formula feeding, hypoxia and cold exposure and decrease the incidence of NEC of neonate rats. It may reduced the apoptosis ratio of intestinal cells and decrease the endogenous production of PAF and TNF-αin intestinal tissue, which would be underlying protective mechanisms of smectite powder on NEC. |
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