目的：探討耐力運動訓練後，腓腸肌 (gastrocnemius) 與比目魚肌 (soleus)不同重鏈肌凝蛋白 (myosin heavy chain, MyHC) 異構物與細胞凋亡現象及粒腺體訊息傳遞分子mRNA 基因表現量的關係。方法：將8 週齡雄鼠(Sprague-Dawley) 隨機分成控制組 (n = 6) 及運動組 (n = 6)，運動組在動物跑步機上進行10 週之耐力運動訓練。結果：耐力運動訓練增加腓腸肌及比目魚肌之檸檬酸合成酶活性 (p < .05)；腓腸肌增加MyHC I、MyHC IIa 與MyHC
IIx 及減少MyHC IIb 的比率 (p < .05)，比目魚肌增加MyHC I 及減少MyHC IIa的比率 (p < .05)；減少腓腸肌與比目魚肌之細胞凋亡現象 (p < .05)，而且比目魚肌細胞凋亡現象低於腓腸肌 (p < .05)；腓腸肌增加B 細胞淋巴瘤/白血病2 (B-cell leukemia/lymphoma 2, Bcl-2) 及減少細胞凋亡誘發因子 (apoptosisinducing factor, AIF) mRNA 表現量 (p < .05)，比目魚肌增加Bcl-2、Bcl-2-性關聯蛋白 (Bcl-2-associated X protein, Bax) 與熱休克蛋白70 (heat shock protein 70, HSP70) 及減少劊白酶9 (caspase-9) 與AIF 等mRNA 表現量 (p< .05)。結論：（一）耐力運動訓練增加腓腸肌及比目魚肌之MyHC I 比率，與骨骼肌細胞凋亡現象及其粒腺體訊息傳遞分子mRNA 基因表現量下降有關，此現象對比目魚肌的影響大於腓腸肌。（二）耐力運動訓練後之比目魚肌，除了可降低粒腺體誘發細胞凋亡訊息傳遞分子mRNA 基因表現量外，同時也會增加抗細胞凋亡分子之mRNA 基因表現量，在腓腸肌無此現象。

Purpose: To examine the relationship between myosin heavy chain (MyHC)
isoforms and apoptosis in the gastrocnemius and soleus after endurance exercise training. Methods: Male Sprague-Dawley rats were randomly assigned to an untrained (CON, n = 6) or an endurance training group (ET, n = 6). The ET exercised on a treadmill for 10 weeks. Results: After endurance exercise traning, citrate synthase activity was increased in both gastrocnemius and soleus (p < .05). In gastrocnemius,the content of MyHC I, MyHC IIa and MyHC IIx were increased while MyHC IIb was decreased (p < .05). In soleus, the content of MyHC I was increased while MyHC IIa
was decreased (p < .05). Apoptotic index was decreased in both astrocnemius and soleus. Also, the apoptotic index of soleus was lower than the gastrocnemius after endurance training (p < .05). B-cell leukemia/lymphoma 2 (Bcl2) mRNA was up-regulated while apoptosis inducing factor (AIF) mRNA was down-regulated in gastrocnemius of ET. Bcl-2, Bcl-2-associated X protein (Bax) and heat shock protein 70 (HSP 70) mRNA were up-regulated while caspase-9 and AIF mRNA were down-regulated in soleus of ET. Conclusions: 1) Decreased apoptosis and down-regulated the mRNA expression of mitochondrial dependent apoptotic signaling were correlated with that the content of MyHC I increased in both gastrocnemius and
soleus after endurance exercise training that is more sensitive to influence soleus than gastrocnemius. 2) Endurance exercise training not only down-regulated the mRNA of mitochondrial dependent apoptotic signaling but up-regulated the mRNA of anti-apoptosis in soleus that didn’t occur in gastrocnemius.