The Protection And Mechanism Of Heat Shock On Skeletal Muscle Against Strenuous Exercise In Rats

Research has established that strenuous,unaccustomed exercise damages skeletal muscle ultrastructure ,and this damage is accompanied by decreased muscle performance. This damage may badly affects the ability of athlete and heavy loader .Now there are several means to prevent and cure this damage,but the effects of all these means are not conformed .So it has become the key task in the sport- medcine field to find out the useful methods to prevent and cure the skeletal muscle damage postexercise.Heat shock response is a rapid and transient cellular reaction to hyperthermia and other stress such as hypoxia and heavy metal .This response involves the preferential transcription of a- set of genes and subsequent translation of a set of proteins calls "heat shock protein",especially HSP70. Extensive research indicates HSP70 has some important functions such as molecular chaperones ,antioxidant ,inhibit apoptosis.Investigations have demonstrated that HSP70 has a phenomenon known as "cross-tolerance".This means that HSP70 raised by one form of sublethal injury seem capable of protecting against a subsequent but different injury.Now the majority of research is focused on cardiorprotection against ischemia by heat shock.There has none report about the protection of skeletal muscle against strenuous exercise by heat shock.The purpose of this study is to examine whether heat shock can protect skeletal muscle against strenuous exercise and improve the skeletal muscle recovery,then to find out the mechanism under this phenomenon .1. The whole body heat shock protect rats skeletal muscle against strenuous exerciseMale SD rats were divided randomly into eight groups.: 1. heat,con(hc);2. heat,0hpostexercise(he0);3.heat,24hpostexercise(he24);4.heat,48h postexercise(he48);5.shem,con(sc);6.shem,0h(se0)postexercise;7. shem,24hpostexercise(se24) ; 8. shem,48hpostexercise(se48). All these rats of heat groups were subjected to whole-body hyperthermia at 40.5-41.5C for 10-15 minutes. Rats were allowed to recovery from whole-body hyperthermia for 24 hours . Skeletal muscle were obtained from rats of groups hs and sc at 24 hours after heat shock to verify expression of HSP70;And HSP70 expression was much higher in he compared with sc.The effects on the muscle damage of running on a treadmill on a 0?at27m min-1 for 90 min were assessed by following postexercise changes in l)plasma activities of CK and LDH 2)histological appearance of muscles. The data indicate the following :l)Compared with the sc group, all exercise protocols of plasma enzymes resulted in significant increasing immediately and 24 hours after running .Yet 48hs after exercise all protocols returned to the pre-exercise level except that the activity of LDH of s48 was much higher compared with postexercise .2)The activity of plasma CK and LDH in the heo group were significantly decreased compared with seO group(p<0.05), the same responses were also found in groups of he24 and se24 (p<0.05).However, the activity of plasma CK and LDH has no significant difference between the he48 and se48,48 hours after exercise.3)The ultrastructural changes 24h after exercise were obviously between he24 and se24 which was quantitated by the percentage of abnormal Z-band .The abnormal rate of Z-band in heO had no significant difference compared with seO.The same result was found in he48 group and se48.These findings demonstrate that heat shock pretreatment can protect skeletal muscle against strenuous running and can improve recovery of the damage of skeletal muscle postexercise. And the protection of heat shock pretreatment may be related to the amount of HSP70-induced.2.The mechanism for the protection of skeletal muscle against strenuous exercise after heat shockIn the first part of study has documented that significant protection can be obtained in skeletal muscle subjected to exercise damage after hyperthermia.In skeletal muscle from hyperthermia-treated rats.CK and LDH efflux were reduced,the skeletal muscle ultrastructural damage was alleviated. The g...