Effect Of Hypoxia And Exercise On Muscle Protein Synthesis Via T-AR Pathway

Purpose:To study the effect and mechanism of hypoxia and exercise via T-AR pathway on muscle protein synthesis under simulated "Living high-training low(Hi-Lo)" condition,we tested and analyzed the changes of testosterone,ARmRNA expression,AR content,AR and DNA binding ability, muscle total protein,MHC content.Materials and methods:Male Sprague—Dawley rats were randomly divided into four groups as follow:Normoxia sedentary group,Hypoxic exposure group,Normoxia exercise group,living high training low group (HiLo group).the normoxia sedentary group lived in normoxic environment,hypoxic exposure group made hypoxic exposure for 12h in normobaric hypoxic tent(oxygen concentration 13.6%),Normoxia exercise group took 1h endurance exercise in normoxic environment at daytime,Hiho group was exposured in hypoxia at night after trained at daytime,the mode and duration of the both load were identical to hypoxic exposure group and normoxia exercise group.The samples were collected and tested at the ist,28th day.Results:(1) After 28 days,compared with normoxia sedentary group, the normoxia exercise group' s serum testosterone and muscle testosterone content decreased a little,ARmRNA and AR protein expression increased, AR and DNA binding ability increased(P＜0.01),muscle total protein content enhanced(P＜0.05),MHC content increased significantly (P＜0.01).(2) After 28 days,compared with normoxia sedentary group, the hypoxic exposure group' s serum testosterone and muscle testosterone content respectively decreased significantly(P＜0.05),ARmRNA improved slightly,AR protein expression decreased,AR activity increased much, muscle total protein content enhanced slightly,MHC content decreased slightly.(3) After 28 days,compared with normoxia exercise group,the HiLo group' s serum,muscle testosterone content decreased,ARmRNA decreased,both AR protein expression and AR activity decreased significantly(P＜0.05),both muscle total protein content and MHC content decreased significantly(P＜0.05),the wet weight of gastrocnemius decreased,body weight decreased significantly(P＜0.05).(4) The changes of muscle testosterone content in each group were similar to the changes of serum testosterone concentration.Conclusions:(1) The selected mode of endurance exercise was profit for muscle protein synthesis,based on it,it is feasible to study the regulated mechanism of protein synthesis in simulated HiLo condition.(2) Muscle protein synthesis and recovery was decreased much via each leval of testosterone,AR protein content,AR activity in HiLo group than normoxia exercise group.Hypoxia after exercise inhibited muscle protein synthesis and caused the decresing of muscle weight and body weight.(3) Hypoxic exposure,normoxia exercise,HiLo regulated AR protein content by changing serum and muscle testosterone leval,and infulenced muscle protein content finally.(4) Concentration of serum testosterone may reflect the variation of muscle testosterone content.