Effects Of 4-week Sodium Nitrate Supplementation On The Expression Of CHOP And Its Downstream Proteins In Rats With One-shot Exhaustion

Objective:Through 4-week nitrate supplementation,this study observed the changes of cell apoptosis related indicators mediated by endoplasmic reticulum stress of extensor longus muscle after a single exhaustion exercise in rats,so as to provide experimental basis for supplementation of exogenous nitrate to improve the mechanism of sports injury.Methods:40 8-week-old male SD rats were randomly divided into the control group（C）,the exercise control group（EP）and the exercise gavage group（EN）,sodium nitrate（sodiumnitrate,Na NO₃）chosen as the exogenous nitrate for gavage,and then the EN group was divided into the low-dose Na NO₃group（ELN）,the medium-dose Na NO₃group（EMN）and the high-dose Na NO₃group（EHM）according to the different gavage concentration,with 8 rats in each group and 5 groups in total.After 3days of adaptive feeding,the rats were weighed and treated by daily gavage according to their weight,and the supplementation concentration of Na NO₃in the ELN,EMH and EHN was 25.5 mg/kg BW/d、59.5 mg/kg BW/d and 85.0 mg/kg BW/d,normal saline of the same dose was given to C and EP for 4 weeks.The day after the completion of the sodium nitrate supplement,the centrifuge platform training of one-time exhaustion was conducted.The slope was-16°,the speed was 16m/min,and the exercise reached exhaustion and the time was recorded.After 24 hours of exercise,blood and extensor digitorum longus muscle were collected for testing.Paraffin sections and HE staining of extensor digitorum longus were prepared to observe the changes of tissue morphology and structure of extensor digitorum longus;Colorimetry was used to detect NO,NO₂^-,CK,Mb and NO concentrations in serum samples;Protein expressions of CHOP,DR5 and Caspase-3 were detected by western blot.Results:（1）4-week nitrate supplementation can prolong the time of one-time exhaustive exercise in rats,and the effect increased with the dose increase.The results were most significant in the groups of 59.5 mg/kg BW/d and 85.0 mg/kg BW/d.（2）4-week nitrate supplementation can improve the serum NO and NO₂^-levels in rats,and increase the concentration of NO in extensor digitorum longus muscle.The higher the dose,the more significant the effect was,and the 85.0 mg/kg BW/d group had the most significant effect.（3）4-week nitrate supplementation can reduce CK activity and Mb content in serum 24h after one-time exhaustion in rats,the injury of extensor longus muscle was alleviated,and the effect increased with the dose,with the most significant effect in the 85.0 mg/kg BW/d group.（4）The expressions of CHOP,DR5 and Caspase-3 were significantly up-regulated at 24h after strenuous exercise.4-week nitrate supplementation can down-regulate the expressions of CHOP and Caspase-3 24h after one-time depletion of extensor digitalis longus in rats,and the effect increased with the dose,with the most significant effect in the 85.0mg/kg BW/d group.The expression of DR5 was not affected.Conclusion:4-week nitrate supplementation can improve the available level of NO in rats.By down-regulating the expressions of CHOP and caspase-3,the injury of the extensor longus muscle of the toe can be improved,the motor ability of the rats can be improved.