Protective Effects Of Bificobacterium Longum And Roles Of PAF And TNF-α On Neonatal Rat Model Of Necrotizing Enterocolitis

Objective Necrotizing enterocolitis(NEC) is a severe emergency as well as the first cause of death in neonate. In spite of extensive epidemiological, clinical, and basic research, there is not preventative treatment for this disease. Whether bificobacterium longum would be helpful to inhibit intestinal injury of NEC and this protection was related to the decrease of contents PAF and TNF-a in intestinal tissue remained unknown. This research investigated the effect of bificobacterium longum on intestinal histopathological changes and the production of platelet-actvating factor(PAF) and tumor necrosis factor-alpha(TNF-a) in neonatal SD rat model of necrotizing enterocolitis.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 from mother rats and feeding with rat milk substitute, hypoxia(100%N2) for 90 second and 4°C cold exposure for 10 minutes, twice a day during 3 consecutive days.Rats in group A was given bifido- bacterium longum(0.4×10⁸CFU/day) 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 bifidobacterium longum(0.4×10⁸CFU/ day) and those in group C was not. On the 4^th day all the subjects were sacrificed and intestinal tissue were obtained to examine.The intestine around ileocecal junction was for histological analysis and score. The remaining intestine was used to measure the content of PAF, TNF-a in homogenate of intestinal tissue. The histopatholigical changes were scored as 0(normal villi), 1 (epithelial cell sloughing), 2(midvillous necrosis), 3(complete villous necrosis), or 4(transmural necrosis) in double-blind way. The mean score more than 2 were considered NEC. The contents of PAF, TNF-a in homogenate of intestinal tissue were measured by ELISA(Kits bought from Shanghai Langka Company), and the contents of PAF, TNF-a in homogenate of intestinal tissue were expressed pg per mg protein of intestinal tissue. Kruskal-Wallis H test, factorial ANOVA and X² Fisher's exact test were used to analyze difference among various groups. a=0.05 was considered significant.