Danieli-Betto D, Betto R, Megighian A, Midrio M, Salviati G, Larsson L
Institute of Human Physiology, University of Padova, Italy.
Acta Physiol Scand. 1995 May;154(1):59-64. doi: 10.1111/j.1748-1716.1995.tb09886.x.
Calcium release activity of sarcoplasmic reticulum and enzyme-histochemical properties were investigated in extensor digitorum longus (e.d.l.) and soleus muscles in young (4 months and old (24 months) male rats. With age, the caffeine threshold concentration for calcium release from the sarcoplasmic reticulum of soleus skinned muscle fibres showed only minor modifications. On the other hand, in e.d.l. skinned muscle fibres, the caffeine threshold concentration decreased significantly (P < 0.05). The histochemical fibre type composition changed with age both in soleus and in e.d.l. muscles, showing a common transformation toward a more oxidative histochemical profile. In fact, in aged soleus, a significant (P < 0.05) increase was observed of type 1 fibres to represent almost the totality of the muscle fibres (more than 98%), while types 2C and 2A were reduced in proportion. In aged e.d.l. the percentage of type 1 (P < 0.05), 2A and 2X (a recently identified fourth component of the fast-twitch muscle types) fibres increased, with a reduction of type 2B (P < 0.01) fibres. The present results suggest that the changes in contractile properties of aged muscles may be related to the changes not only in fibre composition but also in the mechanism of calcium release from sarcoplasmic reticulum.
研究了年轻（4个月）和老年（24个月）雄性大鼠的趾长伸肌（e.d.l.）和比目鱼肌中肌浆网的钙释放活性及酶组织化学特性。随着年龄增长，比目鱼肌去皮肤肌纤维肌浆网释放钙的咖啡因阈值浓度仅有轻微变化。另一方面，在趾长伸肌去皮肤肌纤维中，咖啡因阈值浓度显著降低（P<0.05）。比目鱼肌和趾长伸肌的组织化学纤维类型组成均随年龄变化，呈现出向更具氧化型组织化学特征的共同转变。实际上，在老年比目鱼肌中，观察到1型纤维显著增加（P<0.05），几乎占肌纤维总数的全部（超过98%），而2C型和2A型纤维比例减少。在老年趾长伸肌中，1型（P<0.05）、2A型和2X型（快速收缩肌类型中最近确定的第四种成分）纤维的百分比增加，2B型纤维减少（P<0.01）。目前的结果表明，老年肌肉收缩特性的变化可能不仅与纤维组成的变化有关，还与肌浆网钙释放机制的变化有关。
