Effect Of HSP70 Expression Induced By Hyperthermic Pretreatment On The Antioxidant Ability And Resistance To Damage In The Organism

Heat shock proteins or stress proteins are considered to play an essential role in protecting cells from stress,repairing and maintaining protein folding and preparing them to survive new environmental challenges.HSP70 overexpression induced by heat stress is able to provide thermotolerance.This induces cellular adaptations which enable the organism to better deal with any future exercise challenge.Previous studies have demonstrated that a single exercise bout is capable of increasing HSP70 content.The purpose of this study was to observe HSP70 change after an incremental exhaustive bout of exercise,and HSP70 change postexercise after previous hyperthermic treatment.At the same time we examined antioxidant capacity and damage of organism and analyzed protection of HSP70 overexpression induced by hyperthermic pretreatment.10 male subjects of physical education department ran on a treadmill until exhaustion .Blood was sampled from forearm vein at rest,immediately postexercise,3h and 8h after exercise.These samples were analyzed for leucocytes HSP70 with Western dot blotting.Malonaldehyde (MDA) as a marker of lipid peroxidantion and plasma superoxide dismutase (SOD) were measured at rest,immediately postexercise and 3h after exercise. In addition,plasma creatine kinase(CK)was measured at rest and immediately postexercise as a crude marker of tissue damage.After a week the hyperthermic pretreatment was performed for an hour ( Sauna,45 癈 ;relative humidity,90%) .And then the subjects were at rest under the normal temperature for 24 hours.The same bout of exercise took place after this.The results were as follows: ( 1 ) HSP70 content in human leucocytes remained unchanged immediatelypostexercise and increased respectively from rest at 3h after exercise. It indicated that a single short-term exhaustive bout of exercise was able to increase leucocyte HSP70 expression. And it returned to pre-exercise level until 8h after exercise. HSP70 expression increased significantly at 24h after hyperthermic pretreatment.Compared with the level immediately postexercise before hyperthermic treatment,HSP70 decreased significantly immediately postexercise.HSP70 content at 8h after hyperthermic pretreatment decreased respectively compared with the basal line.This demonstrated that probably the adaptive response of the basal HSP expression took place.(2) SOD activity in plasma elevated significantly immediately after exercise.There were no significant differences between before hyperthermic treatment and after hyerthermic pretreatment.It is concluded that HSP70 overexpression induced by hyperthermic treatment is not able to enhance SOD activity in plasma.(3) Plasma MDA content increased respectively immediately postexercise.MDA elevated significantly immediately postexercise after hyperthermic pretreatment and it was lower respectively than that immediately postexercise before hyperthermic treatment.We conclude that HSP70 is probably involved in eliminating free radicals .(4) There was significant change of CK activity in plasma immediately after exercise. Plasma CK activity remained unchanged immediately postexercise after hyperthermic pretreatment,but was lower respectively than that immediately postexercise before hyperthermic treatment.This result demonstrates that HSP70 overexpression induced by hyperthermic treatment probably enables the organism to enhance the capacity of resistance to damage induced by exercise .(5) There were no significant differences in blood lactate,VO2max and exercise time.This indicates that HSP70 is not able to increase tolerance to a single short-term exhaustive exercise.