Homsher E
Annu Rev Physiol. 1987;49:673-90. doi: 10.1146/annurev.ph.49.030187.003325.
During a maintained tetanus most of the energy liberated is produced by ATP hydrolysis at the cross-bridge. The energy produced by ATP hydrolysis by the sarcoplasmic reticulum is, however, a significant fraction (0.35) of the total. The energy liberation rate depends on a variety of factors (including the shortening velocity, sarcomere length, temperature, fiber type, and duration of contraction) and is, for the most part, consistent with current cross-bridge models. At the beginning of tetanic stimulation, a significant amount of heat (approximately 30 mJ/g) is produced by calcium binding reactions in the sarcoplasm. In the transition from an isometric to a shortening contraction, the cross-bridge cycling rate increases, and as much as 6 mJ/g of unexplained heat is produced. This unexplained heat appears to involve enthalpy changes accompanying a redistribution of cross-bridge intermediates, and it is reversed by high-energy phosphate splitting after the cessation of shortening. The mechanistic significance of these enthalpy changes remains to be elucidated.
在持续强直收缩期间，释放的大部分能量是由横桥处的ATP水解产生的。然而，肌浆网ATP水解产生的能量占总量的相当一部分（0.35）。能量释放速率取决于多种因素（包括缩短速度、肌节长度、温度、纤维类型和收缩持续时间），并且在很大程度上与当前的横桥模型一致。在强直刺激开始时，肌浆中的钙结合反应会产生大量热量（约30 mJ/g）。从等长收缩转变为缩短收缩时，横桥循环速率增加，会产生高达6 mJ/g的无法解释的热量。这种无法解释的热量似乎涉及伴随横桥中间体重新分布的焓变，并且在缩短停止后通过高能磷酸键断裂而逆转。这些焓变的机制意义仍有待阐明。
