| Research Abstract |
後肢ギプス固定モデルラットを用いて,再荷重前の熱刺激が再荷重による筋傷害に与える影響について検討した.ラットを対照群と実験群に分け,実験群は4週間ギプス固定し再荷重する再荷重群と,同様にギプス固定し熱刺激を行った後に再荷重する熱刺激群を設定した.検索時期は再荷重から0,1,3,5日目とし,ヒラメ筋を採取してHeat Shock Protein(HSP)70含有量と壊死線維数を計測した.HSP70含有量は0日目のみ熱刺激群が再荷重群より有意に高値を示した.壊死線維数は,全ての検索時期で対照群に比べ再荷重群と熱刺激群は有意に高値を示した.さらに,再荷重群と熱刺激群を比べると,3日目では熱刺激群が再荷重群より有意に低値を示し,5日目では熱刺激群が再荷重群より有意に高値を示した.再荷重前の熱刺激によって,再荷重時の骨格筋にHSP70が誘導され,再荷重から3日目の筋傷害が抑えられた.しかし,1度の熱刺激だけでは,長期的な筋傷害の予防効果は得られなかった.
The purpose of this study was to determine whether heat stress is preventive for muscle fiber injury induced by reloading after immobilization in rat soleus muscle. Forty-five male 8-week-old Wistar rats were used. Rats were divided randomly into control (C, n=15), immobilized followed by normal recovery (IR, n=15), and immobilized followed by heat stress before reloading (IH, n=15) groups. Bilateral ankles of each rat in the IR and IH groups were fixed in full planter flexion with a plaster cast for 4 weeks. Immediately after 4 weeks of immobilization, reloading was permitted in the IR group. Rats in the IH group were first exposed to heat stress (41 ℃ for 60 min) in an incubator under anesthesia 2 days before reloading. At 0, 1 and 3 days after reloading, both soleus muscles in all groups were excised for histopathological and biochemical analyses. Immediately after remobilization, Hsp70 levels were significantly increased in IH groups compared with IR groups. In 3 days after reloading, the number of necrotic muscle fibers was significantly increased in IR compared with IH groups. The present findings suggest that heat stress prior to reloading induces expression of Hsp70 and leads to protective effect against soleus muscle injury induced by reloading after immobilization.
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