Metzger J M, Moss R L
Department of Physiology, School of Medicine, University of Wisconsin, Madison 53706.
Biophys J. 1988 Dec;54(6):1169-73. doi: 10.1016/S0006-3495(88)83052-2.
Previous studies on skinned muscle fibers have demonstrated a direct effect of elevated levels of H+ ion to depress force production; however, the molecular basis for this effect is presently unknown. Here, whole troponin complexes were removed from skinned single fiber preparations of rat slow-twitch and fast-twitch muscles, and the effect of H+ ions on the resultant Ca2+-insensitive force was examined. The effect of H+ ions to depress force was found to be virtually identical in untreated control fibers activated in the presence of Ca2+ and in fibers activated in the absence of Ca2+ by troponin removal. Thus, the effect of H+ ions to depress force occurs at a step in activation beyond the disinhibition of the thin filament by Ca2+, probably involving reductions in the number of attached cross-bridges or in the force per attachment.
以往对去皮肤肌纤维的研究表明，H⁺离子水平升高会直接抑制力的产生；然而，这种效应的分子基础目前尚不清楚。在此，从大鼠慢肌和快肌的去皮肤单纤维制剂中去除了完整的肌钙蛋白复合物，并研究了H⁺离子对由此产生的Ca²⁺不敏感力的影响。结果发现，在有Ca²⁺存在时激活的未处理对照纤维以及通过去除肌钙蛋白在无Ca²⁺情况下激活的纤维中，H⁺离子抑制力的效应几乎相同。因此，H⁺离子抑制力的效应发生在激活过程中Ca²⁺解除细肌丝抑制作用之后的一个步骤，可能涉及附着的横桥数量减少或每个附着点的力降低。
