| Digestive system disease is a common disease of air force pilots,and its pathogenesis is closely related to its specific occupational factors.Positive acceleration(+Gz)has become an important factor that affects flight safety.There have been a lot of researches about the effects of +Gz exposure on systemic tissues,however,few studies have reported on intestinal barrier.It has been proved that intestinal barrier dysfunction not only affects the digestive absorption function,but also plays an important role in systemic diseases such as severe infection,trauma,shock and so on.The mechanical barrier and immune barrier are the most important components of the intestinal barrier,it is also a hot spot in recent years.In this study,we investigated the effects of different +Gz exposure on mechanical barrier and immune barrier.The normal function of intestinal mechanical barrier mainly depends on the integrity of tight junctions between intestinal epithelial cells.When the integrity of intestinal mucosa is damaged and the permeability increased,the levels of D-lactic acid and diamineoxida in serum will be also significantly increased.Secretory immunoglobulin A is the main factor of intestinal mucosal immunity,it plays an important role in intestinal mucosal immune defense,and can better reflect the intestinal mucosal immune function.D-LAC,DAO and sIgA levels are good indicators for evaluating intestinal mechanical barrier and immune barrier.Glutamine is an essential amino acid,which provides about 70% of energy for the intestinal tract.It is of great significance for the recovery of intestinal barrier dysfunction.In this study,rats were selected as the subjects,simulated different +Gz values by special animal centrifuge,and given Gln for intestinal protection.Through the detection of the levels of D-LAC,DAO and sIgA in intestinal mucosa of rat,investigate the effects of +Gz exposure on intestinal barrier function in rats and the protective effect of Gln on intestinal barrier,provide experimental basis for the prevention of pilot intestinal disease.In the experiment,32 male SD rats were randomly divided into 4 groups,each group has 8 rats,which were labeled as A?B?C?D group.Group A was normal control group,group B was +5Gz group,group C was +10Gz group,group D was glutamine&+10Gz value group.Simulated different +Gz values by animal centrifuge,rats in group A were fixed at the end of the centrifuge arm for 5min,rats in group B were rotated at +5Gz for 5 min,rats in group C were rotated at +10Gz for 5 min,rats in group D was drenched Gln solution 10 ml before +Gz exposure,the supplementary dose was 1.5g/kg,and the training method was the same as group C.The experimental time is am 9:00-11:00 and it lasts 5 days.After the experiment,the rats were anesthetized at the following day,rat intestinal mucosa specimens and peripheral serum were obtained,the histomorphology characteristics of small intestine in rats were observed under microscope,the peripheral blood serum levels of D-LAC,DAO and the content of sIgA in intestinal mucosa were detected.Test results show: 1.The gross observation of the small Intestinal tissue of rats in each group and morphological characteristics of small intestinal mucosa under light microscope.The intestinal mucosa of rats in group A was pale red,the surface was smooth and complete,and there was no congestion,edema,no hemorrhage and erosion.Small samples of B,C group could be seen scattered bleeding point and hemorrhagic zone.In group D,the small intestine tissue was smooth and complete,but small bleeding points could be scattered.The small intestine of the rats in each group were made pathological sections,and stained with HE.There was no obvious abnormality of intestinal mucosa in group A,and no obvious infiltration of inflammatory cells.The intestinal mucosa of B,C,D rats can be seen that the villus space is widening,the height was shortened,the transverse diameter was widened,and the arrangement was disordered.There was a massive inflammatory cell infiltration,and the injury degree of group C was significantly higher than that of group B and group D.The results showed that +Gz exposure could damage the intestinal mucosa of rats,and the greater the exposure value of +Gz,the more serious the injury was,Gln as a mucosal protective agent could effectively reduce the damage level of +Gz exposure on intestinal mucosa.2.Comparison of serum DAO and D-LAC levels in rats exposed to different doses of +Gz.Compared with the control group,the serum DAO,D-LAC levels of group B and C were significantly higher(p<0.05),these results indicated that +Gz exposure can damage the intestinal mechanical barrier in rats.The level of DAO in group C was significantly higher than that of group B(p<0.05).The results showed that the mechanical barrier injury in high dose +Gz exposure group was more serious than that in low dose +Gz exposure group.3.Comparison of sIgA level in intestinal mucosa of rats exposed to different doses of +GzCompared with the control group,the sIgA level of intestinal mucosa in group B and group C decreased obviously,and the difference was significant(p<0.05).The sIgA level of intestinal mucosa in group C was significantly lower than that in group B(p<0.05).These results indicated that +Gz exposure could damage the intestinal mucosal immune barrier in rats,and the damage degree of immune barrier in high dose +Gz group was worse than that in low dose +Gz exposure group.4.The protective effect of Gln on intestinal mucosal barrier.The serum DAO and D-LAC levels in group D were significantly lower than those in group C(p<0.05).The sIgA level of intestinal mucosa was significantly higher than that of +10Gz group(p<0.05).The results indicated that as an important nutrient,Gln could effectively reduce the damage of +Gz exposure on intestinal mechanical barrier and immune barrier.In conclusion,+Gz exposure can damage the intestinal mucosa of rats,the mechanism may be related to weaken the protection ability of the intestinal mechanical barrier and immune barrier,and the intestinal barrier damage level of high +Gz exposure dose was higher than that of the low dose group.The treatment of Gln before exposure to +Gz can effectively reduce the damage of intestinal mechanical barrier and immune barrier.It is suggested that Gln can be used to protect the intestinal barrier during flight training,and improve the quality of flight. |
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