| Objective:To establish a rat model of exertional heat stroke,to detect the related indicators of the intestinal mucosal barrier,and to explore the effects of movement under the enviroment of hyperthermia and high humidity on the intestinal mucosal barrier function in rats.Methods:Establish a rat model: After running training,30 rats which exercised correctly on the treadmill were selected,they were randomly divided into three group:the normal control group;the normal temperature and humidity excercise group and the hyperthermia and high humidity exercise group,each consisting of 10 rats.In the experimental temperature of 35±2℃ and the humidity of 80±10%,rats in the hyperthermia and high humidity exercise group ran at a speed of 28m/min.The rectal temperature reaching the standard means that the rat model of exertional heat stroke was successfully established.In the experimental temperature of 25±2℃ and the humidity of 60%,rats in the normal temperature and humidity exercise group ran at a speed of 28m/min.The time to exercise of this group rats was randomly matched the hyperthermia and high humidity exercise group.Rats in the normal control group was fed as usual without running.Detect the related indicators:(1)The plasma endotoxin(LPS),diamine oxidase(DAO)and D-lactate(DLAC)concentrations of the rats were detected by enzymelinked immunosorbent assay(ELISA).(2)Hematoxylin-eosin stained sections of ileum mucosal tissue were examined under an optical microscope to assess pathological changes.(3)The faecal samples were sequenced by16 S r RNA to analyze the abundance and diversity of different groups of gut microbiota.Results:(1)All rats in the hyperthermia and high humidity exercise group experienced exertional heat stroke,The anal temperature of all rats was over 42.5℃.Their anal temperature was 42.6±0.1℃,running time was 48.5±18.3minutes.In the same exercise time,the anul temperature of the rats in the normal temperature and humidity excercise group was 38.4±0.5℃,the difference was statistically significant(t=25.1,P<0.001).(2)The plasma LPS levels of the normal control group were 1258.981±278.233 pg/ml,the normal temperature and humidity exercise group were 2024.115±373.512 pg/ml,and the hyperthermia and high humidity exercise group were 2459.268± 448.608pg/ml,there were significantly different among the three groups(F=26.490,P <0.001).The plasma LPS levels were significantly increased after exercise,compared with the normal control group,the levels were increased both in the normal temperature and humidity exercise group and the hyperthermia and high humidity exercise group,the differences were statistically significant(P<0.001,P<0.001).The plasma LPS levels in the hyperthermia and high humidity exercise group were increased compared with the normal temperature and humidity rest group,the difference was statistically significant(P=0.038).(3)There were differences in the plasma DAO and DLAC levels among the three groups(DAO Welch F=173.524,P <0.001,DLAC Welch F=14.318,P <0.001).The plasma DAO levels were significantly increased after exercise,compared with the normal control group,the levels were increased both in the normal temperature and humidity exercise group and the hyperthermia and high humidity exercise group,the differences were statistically significant(452.047±180.601 vs 287.404±38.688,P=0.045,885.138±91.546 vs287.404±38.688,P <0.001).The plasma DLAC levels were significantly increased after exercise,compared with the normal control group,the levels were increased both in the normal temperature and humidity exercise group and the hyperthermia and high humidity exercise group,the differences were statistically significant(1.502±0.211 vs 1.308±0.081,P=0.048,1.911±0.375 vs 1.308±0.081,P<0.001).The plasma DAO levels and DLAC levels in the hyperthermia and high humidity exercise group were both increased compared with the normal temperature and humidity exercise group,the differences were statistically significant(DAO P<0.001,DLAC P=0.024).(4)Compared with the normal control group and the normal temperature and humidity excercise group,the intestinal mucosal tissue of the rats in the hyperthermia and high humidity exercise group was swelled,part of the epithelium was necrosis and exfoliation and partial villus height decreased.(5)The α-diversity reflect the richness and diversity of the microbiota in the intra group sample.The ACE and the chao 1 index were used to estimate the bacterial abundance,higher values indicate higher richness.Through the ACE and the chao 1 index found that,whether compared with the normal control group or the normal temperature and humidity group,the flora abundance in the hyperthermia and high humidity group were increased,the differences were statistically significant(ACE P=0.018,P=0.027,chao 1 P=0.007,P=0.01),while the flora abundance in the normal temperature and humidity group were slightly more than the normal control group,and the difference was not statistically significant(ACE P=0.983,chao 1 P= 0.968).The shannon and simpson index were used to estimate the bacterial diversity,higher values indicate higher diversity.Compared the three groups,there were no significant difference in the the shannon and the simpson index,and the difference were not statistically significant(P>0.05).Then we compare the β-diversity of the intestinal flora among the three groups,through PCo A analysis we found that the three groups samples formed clusters with their own characteristics.The intestinal microflora at the hyperthermia and high humidity exercise group changed significantly.At the level of the door,the abundance of Proteobacteria was increased,at the level of the door,the abundance of Streptococcaceae and Enterobacteriaceae were significantly increased,while the abundance of Lactobacteriaceae and Bifidobacteriaceae were significantly decreased,and at the level of the genus,the abundance of Citrobacter and Streptococcus were significantly increased,while the abundance of Lactobacillus and Bifidobacteria were significantly decreased(P<0.05).Compared with the normal control group,the abundance of Streptococcaceae and Enterobacteriaceae at the normal temperature and humidity exercise group had the trend of increasing,and the abundance of Lactobacteriaceae and Bifidobacteriaceae tended to decrease.Conclusion:1.The plasma DAO and DLAC levels of the rats in the hyperthermia and high humidity exercise group were significantly increased,it was suggested that intestinal mucosal injury and increased permeability are the important ways of intestinal endotoxemia.2.The rats in the hyperthermia and high humidity exercise group had increasing intestinal mucosal permeability and the disorders of intestinal flora which was showed that the decreasing proportion of beneficial bacteria such as Lactobacteriaceae and Bifidobacteriaceae and the increasing proportion of harmful bacteria such as Enterobacteriaceae.And occurred the endotoxemia,it means that intestinal mucosal barrier function damage is one of the important pathogenesis of the exertional heat stroke. |
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