Homsher E, Kean C J
Fed Proc. 1982 Feb;41(2):149-54.
Energy balance experiments, testing the hypothesis that the observed enthalpy production can be accounted for by high-energy phosphate splitting, have shown that two additional sources of heat production not directly associated with high-energy phosphate splitting per se can be observed during contraction. The first is an energy production occurring during the first 5 s of a maintained isometric tetanus (0 C), which amounts to about 25 mJ/g of muscle. Because the amount of this unexplained enthalpy is not altered by varying the amount of thick and thin filament overlap, it is suggested that it is associated with Ca2+ redistribution (and related binding) within the muscle cell during contraction. The second type of unexplained enthalpy production, amounting to 5-8 mJ/g, occurs when thick and thin filaments slide rapidly past one another. It is suggested that its production is associated with a redistribution of cross-bridge states upon transition from isometric to rapidly shortening contraction. Both types of unexplained enthalpy production are thought to be reversed by an ATP splitting subsequent to their production.
能量平衡实验对“观察到的焓产生可由高能磷酸键断裂来解释”这一假说进行了验证，结果表明，在肌肉收缩过程中可观察到另外两种与高能磷酸键断裂本身并无直接关联的产热来源。第一种是在持续等长强直收缩（0℃）的最初5秒内发生的能量产生，约为每克肌肉25毫焦。由于这种无法解释的焓的量不会因粗细肌丝重叠量的变化而改变，因此有人认为它与收缩过程中肌肉细胞内Ca2+的重新分布（及相关结合）有关。第二种无法解释的产热类型，量为每克5 - 8毫焦，发生在粗细肌丝彼此快速滑动时。有人认为其产生与从等长收缩转变为快速缩短收缩时横桥状态的重新分布有关。这两种无法解释的产热类型都被认为在产生后会因ATP的分解而逆转。
