Chapman J B, Gibbs C L
Biophys J. 1972 Mar;12(3):227-36. doi: 10.1016/S0006-3495(72)86082-X.
Initial energy utilization in the twitch is visualized as the result of the activity of two distinct processes. The first is the calcium-pumping activity of the sarcoplasmic reticulum, which has a constant energy requirement under normal conditions. The second is the chemomechanical transduction process consisting of a variable number of quantal contractile events, each with a fixed enthalpy equal to the molecular enthalpy of adenosine triphosphate (ATP) hydrolysis in vivo. This enthalpy appears either as heat or as contractile element work. Total enthalpy varies according to the number of quantal contractile events that occur in the twitch cycle. The basis of the variation is suggested to be velocity-dependent activity of the actomyosin ATPase, allowing more quantal events to occur in a contraction cycle when shortening occurs. The classical designation "activation heat" is held to be appropriate for the first process. The partition of the enthalpy of the second process that is currently in vogue is held to be misleading and a new formulation is suggested in which the properties of the quantal contractile event are reflected in general terms. The formulation of the proposed transduction model represents a conceptual return to the viscoelastic theory, but at a quantal level. The model can explain the results of the preceding paper and is adaptable to different muscles without having to postulate fundamental differences in energy utilization.
单收缩中的初始能量利用被视为两个不同过程活动的结果。第一个过程是肌浆网的钙泵活动，在正常情况下其能量需求恒定。第二个过程是化学机械转导过程，由可变数量的量子收缩事件组成，每个事件具有固定的焓，等于体内三磷酸腺苷（ATP）水解的分子焓。该焓要么以热的形式出现，要么以收缩元件功的形式出现。总焓根据单收缩周期中发生的量子收缩事件的数量而变化。这种变化的基础被认为是肌动球蛋白ATP酶的速度依赖性活动，使得在发生缩短时，在一个收缩周期中会发生更多的量子事件。传统上称为“激活热”的概念适用于第一个过程。目前流行的第二个过程的焓分配被认为具有误导性，因此提出了一种新的表述方式，其中量子收缩事件的特性以一般术语体现。所提出的转导模型的表述代表了在量子水平上对粘弹性理论的概念回归。该模型可以解释前文的结果，并且适用于不同的肌肉，而无需假定能量利用存在根本差异。
