Effects Of Hypoxic Training On VEGF Expression In Rat Skeletal Muscle After Reoxygenation

Objective: Based on the theory that exercise and hypoxia can regulate hypoxia-inducible factors and vascular endothelial cell growth factor,this paper refines the influence degree and time law of different reoxygenation periods of hypoxic exercise on VEGF expression in rat skeletal muscle by constructing a model of high-live,high-training and low-intensity exercise,and discusses the specific changes of skeletal muscle function in different reoxygenation periods,so as to provide a theoretical experimental basis for the recovery of physiological function in the later stage of altitude training,the adjustment of pre-competition stress level and the preparation stage of lower plateau competition.Methods: The experimental rats were randomly divided into normobic quiet group(NC),normoxic exercise group(NS),and hypoxic quiet group(DC).The hypoxic exercise group was randomly divided into the first day group of high residence and low training reoxygenation(H1),the second day group of high residence and low training reoxygenation(H2),the 4th day group of high residence and low training reoxygenation(H4),and the 6th day group of high residence and low training reoxygenation(H6).The partial pressure of oxygen in the low-pressure oxygen chamber is maintained at 13.2%,which is equivalent to 3500 m in the simulated plateau.The NC group was quietly reared in a normooxygen environment.The NS group performed moderate intensity exercise of 4w,6d/w(Monday to Saturday),1 time/d,50min/time,and 25m/min in normal oxygen environment.The DC group was quietly reared in a low-oxygen environment.All rats in the remaining hypoxia groups were exposed to hypoxic environment for 12 h and normoxic environment for 12 h per day.The training load was exactly the same as that of the NS group in a normoxic environment,and a moderate-intensity training of 50 min per day and a speed of 20 m/min in a low-oxygen environment was added every other day(Tuesday,Thursday,Saturday)for 4 weeks.After the end of 4 weeks,all the rats in the hypobaric oxygen cabin were reared outside the cabin,and the reoxygenation training of the plateau under the end of altitude training was simulated,and the training plan remained unchanged.NC,NS and DC rats were immediately sacrificed after 50 minutes of exercise on the last day of formal training.The H1 group was immediately executed after 50 min of training on the first day after reoxygenation training,the H2 group was immediately executed after 50 min of training on the second day after reoxygenation,the H4 group was immediately executed after 50 min of training on the fourth day after reoxygenation,and the H6 group was immediately executed after 50 min of training on the 6th day after reoxygenation.Outcome:(1)Rat weight: the weight of NS group was significantly lower than that of the control group NC(P<0.01),the growth rate of H1 group,H2 group,H4 group and H6 group was significantly lower than that of control group DC(P<0.01),and the weight of the DC group decreased significantly compared with the NC group after the experiment(P<0.05).(2)Rat HIF-1α: The level of HIF-1αm RNA was H1 group> H2 group> DC group>H4 group> NS group >H6 > from high to low NC Group.Among them,the H1 group was the most obvious,and there were significant differences between the 1(H1 group),2(H2 group)and 4(H4 group)days after hypoxic exercise reoxygenation compared with the normoxic exercise NS group(P<0.05),and the normoxic exercise NS group was elevated compared with the H6 group on the 6th day of hypoxic exercise reoxygenation,but it was not specific.Compared with the normooxygen quiet NC group,the hypoxic quiet DC group had a significant difference(P<0.05).Compared with the normobic quiet NC group,the normobic exercise NS group was elevated,but it was not specific.The levels of HIF-1a protein were H1 group> H2 group> DC group> H4 group>H6 group> NS group > NC group in descending order.Compared with the normoxic quiet NC group,the levels of HIF-1a protein on day 1(H1),day 2(H2),day 4(H4)and day 6(H6)after hypoxic exercise reoxygenation were significantly increased(P<0.05),and the levels of HIF-1a protein on day 4(H4)after hypoxic exercise reoxygenation were lower than those in the hypoxic quiet DC group,which was not specific.(3)Rat VEGF: The level of VEGFm RNA in order from high to low was H1group> H2 group> DC group> H4 group> NS group> NC>H6 group.Among them,the H1 group was the most obvious,and there were significant differences between the 1(H1 group),2(H2 group)and 4(H4 group)days after hypoxic exercise reoxygenation compared with the normobic exercise NS group(P<0.05),and the level of normoxic exercise NS group was higher than that in the H6 group on the 6th day of hypoxic exercise reoxygenation,and it was specific.Compared with the normooxygen quiet NC group,the hypoxic quiet DC group had significant differences(P<0.05).The levels of VEGF protein were H1 group> H2 group> DC group > H4 group >from high to low NS group>NC group > H6 group.Compared with the normoxic quiet NC group,the levels of VEGF protein were significantly increased in the groups after reoxygenation on day 1(H1),day 2(H2),and day 4(H4)after hypoxic exercise(P<0.05).The level of VEGF protein on day 6(H6)after hypoxic exercise reoxygenation was lower than that in the hypoxic quiet DC group and the normoxic quiet NC group,and was not specific.Compared with the normoxic quiet NC group,the level of VEGF protein was significantly increased in the hypoxic quiet DC group(P<0.05).(4)Rat creatine kinase: CK activity was H1 group> H2 group> H4 group> H6group> DC group> NS group > NC group from high to low.Compared with the normoxic quiet NC group,the levels of CK activity on days 1(H1),2(H2),4(H4)and6(H6)after hypoxic exercise reoxygenation were significantly increased(P<0.05).(5)Rat lactate dehydrogenase: LDH activity was H1 group> H2 group> H4 group>H6 group> DC group> NS group > NC group in descending order.Compared with the normoxic quiet NC group,the levels of LDH activity on day 1(H1),day 2(H2),day 4(H4)and day 6(H6)after reoxygenation with hypoxic exercise were significantly increased(P<0.05).Conclusion:(1)The rate of weight gain and change of rats in the high-lived,high-training and low-training group was lower than that of the normoxic training group,and they gradually recovered after reoxygenation.(2)On the first day of reoxygenation training after high residence and high training and low training,the HIF-1α protein and HIF-1α m RNA in the skeletal muscle of rats reached the maximum;The decrease in HIF-1α m RNA on day 6 of reoxygenation was slightly higher than that in the normoxic quiet group,indicating that the hypoxic stimulation effect was not over.The concentration of HIF-1α protein on day 6 of reoxygenation was still higher than that of the control group.(3)On the first day of reoxygenation training after high residence and high training and low training,the expression of VEGF protein and VEGFm RNA in rat skeletal muscle reached the maximum reoxygenation on the 6th day,the expression of VEGF protein and VEGFm RNA was consistent,both lower than that of the normal oxygen quiet control group,and HIF-1α degradation was relatively lost in the control group during the 4-6th day of reoxygenation,so that the skeletal muscle VEGF would not be overexpressed.(4)On the first day of reoxygenation training after high residence and high training,creatine kinase and lactate dehydrogenase activity reached the maximum,and after the start of reoxygenation,the double stimulation of hypoxia and exercise disappeared,and the body still had a higher anaerobic exercise ability than the normoxic exercise group and the hypoxic quiet group,but the level would gradually be lower than the control group after the 6th day of the lower plateau.