Jaspers S R, Fagan J M, Tischler M E
J Appl Physiol (1985). 1985 Oct;59(4):1159-63. doi: 10.1152/jappl.1985.59.4.1159.
One leg of tail-casted suspended rats was immobilized in a plantar-flexed position to test whether chronic shortening of posterior leg muscles affected the metabolic response to unloading. The immobilized plantaris and gastrocnemius muscles of these animals showed approximately 20% loss of muscle mass in contrast to simply a slower growth rate with unloading. Loss of mass of the soleus muscle during suspension was not accentuated by chronic shortening. Although protein degradation in the isolated soleus muscle of the plantar-flexed limb was slightly faster than in the contralateral free limb, this difference was offset by faster synthesis of the myofibrillar protein fraction of the chronically shortened muscle. Total adenine nucleotides were 17% lower (P less than 0.005) in the chronically shortened soleus muscle following incubation. Glutamate, glutamine, and alanine metabolism showed little response to chronic shortening. These results suggest that, in the soleus muscle, chronic shortening did not alter significantly the metabolic responses to unloading and reduced activity.
将大鼠尾巴固定后悬吊，使一侧下肢处于跖屈位，以测试后肢肌肉长期缩短是否会影响对卸载的代谢反应。与单纯卸载时生长速度减慢相比，这些动物被固定的跖肌和腓肠肌肌肉质量损失约20%。比目鱼肌在悬吊期间的质量损失并未因长期缩短而加剧。虽然跖屈肢体分离的比目鱼肌中的蛋白质降解略快于对侧自由肢体，但这种差异被长期缩短肌肉的肌原纤维蛋白部分更快的合成所抵消。孵育后，长期缩短的比目鱼肌中总腺嘌呤核苷酸降低了17%（P<0.005）。谷氨酸、谷氨酰胺和丙氨酸代谢对长期缩短几乎没有反应。这些结果表明，在比目鱼肌中，长期缩短并未显著改变对卸载和活动减少的代谢反应。
