The Establishment And Evaluation Of Food Allergic Models With Young Rats

ObjectiveTo establish and evaluate the food allergic models with SD young rats for ovalbumin(OVA) through sensitized by intraperitoneal injection(i.p) and challenged by gavage, to explore suitable conditions and evaluating methods for food allergic models of young rats.MethodsSixteen female Sprague-Dawley (SD) young rats (three weeks old) were randomly divided into two groups.SD young rats in food allergy (FA) group were sensitined by intraperitoneal injection(i.p)with0.2mL of0.2mg mL-1ovalbumin solution in normal saline injected on days0,2,4,7,9,11. To potentiate the immune response,5mg mL-1AL(OH)3adjuvant mixed with0.2mL of0.2mg mL-1ovalbumin solution was injected on day0. The young rats were challenged by gavage with2.0mL of15mg mL-1ovalbumin solution on days20,24,28,30. Unsensitized countrol rats were i.p and gavaged with the same capacity of normal saline instead of ovalbumin over the same period. The weight growing, the appearances, the activity, the defecation of SD rats were observed By using ethology methods. Blood was taken in angular vein on days0,20,30. Ovalbumin specificity IgE (OVA-IgE) levels in serum were analyzed by Enzyme-linked Immunoassay (ELISA). On day30, rats executed and tissues of the two segments of Jejunum,Ileum and Colon were obtained,one was used to observe the intestinal mucosa forms and Eosinophils by Hematoxylin and Eosin (HE)Staining and using Optical mircroscope, the other (freshtissues) was used to observe mast cells(MC),account the density of MC and the percentage of integrity by frozen section and toluidin blue staining.SPSS13.0software for Windows was used in all statistical tests. The value of a=0.05was considered significant.Result[1]There was no statistical difference respectively in average body weight between the two groups on days0,7,14,21,(P>0.05). On day28>30, the average body weight of FA group was lighter than NS group, there was statistical difference(P<0.05). Most SD rats of FA group displayed bristling and lustreless, seldomly moving, restlessness or diarrhea after challenges. And symptoms above were more and more serious with the increase in the number of challenging. None of that above happened to NS group.[2]The average OVA specificity IgE levels(μg/ml) in serum prior sensitization(DOp),prior the first challenge(D20p),after the last challenge(D30a) were respectively6.19±1.05,10.34±1.28,13.17±1.43,and NS group were6.11±1.13,6.17±1.08,6.31±1.05. In FA group, OVA-IgE levels were gradually more and more high along with sentization and challenges(P<0.05). OVA-IgE levels prior the first challenge(D20p)、,after the last challenge (D30a) in FA group were significantly higher than NS group,respectively(P<0.01). The rate of sensitization after last challenged by gavage was100%by allergic judgment standard(above the average IgE level adding three standard deviation of NS group),and none was sensitized in NS group.[3]The pathomorphological changes of intestines by hematoxylin and eosin (HE)staining with light microscope:In FA group, the intestinal mucous membrane of Jejunum,Ileum,Colon were damaged to some extent. The injury in Jejunum was more serious and more eosinophils(EOS) were aggregated.The intestinal mucous membrane of NS group were complete,and Only few EOS were observed in NS group. The average EOS at high magnification in Jejunum,Ileum and Colon of FA group were respectively26.6±5.9,18.2±3.2,13.0±2.8,those in NS group were respectively7.8±1.4,7.6±1.6,6.2±1.3. Compared with NS group, the EOS of FA group were significantly more(P<0.01).[4]At high magnification, more mast cells(MC) were aggregated in lamina propria of the Jejunums,Ileums and Colons,with cells degranulation in FA group.Only few MC were observed in NS group, with fewer cells degranulation. The average MC at high magnification in Jejunum,Ileum,Colon of FA group were respectively9.8±2.3,5.9±2.0,4.4±1.3, those in NS group were respectively2.3±0.3,2.0±0.4,1.3±0.3. The MC of FA group were significantly more than NS group(P<0.01).In FA group, The percentages of mast cells integrity(%) were respectively22.3±2.6,42.9±4.9,57.5±2.9in Jejunum,Ileum,Colon of FA group;those were respectively80.1±4.6,83.8±4.5,85.1±4.8in NS group, there was statistical difference between the two groups(P<0.01).Conclusion The young rats food allergic models were successfully established through sensitized by i.p low dose OVA mixed with aluminum hydroxide and challenged by gavaging high dose OVA.