Walker J S, Wingard C J, Murphy R A
Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville 22908.
Hypertension. 1994 Jun;23(6 Pt 2):1106-12. doi: 10.1161/01.hyp.23.6.1106.
Ca(2+)-dependent crossbridge phosphorylation is the primary mechanism governing crossbridge cycling in smooth muscle. A four-state crossbridge model in which phosphorylation is the only proposed regulatory mechanism was successful in predicting the mechanical properties of the swine carotid media including latch (sustained force with reduced crossbridge cycling). This model also predicts that the ATP consumption of crossbridge phosphorylation is approximately equal to that of crossbridge cycling and that ATP consumption will rise hyperbolically with increases in steady-state force. This review shows these predictions to be consistent with the available energetics data for the carotid media. The absolute energetic cost of covalent regulation is modest and less than the energy savings associated with latch. However, covalent regulation should reduce the total mechanical efficiency of smooth muscle relative to striated muscle.
钙离子依赖的横桥磷酸化是控制平滑肌横桥循环的主要机制。一个四态横桥模型中，磷酸化是唯一提出的调节机制，该模型成功预测了猪颈动脉中膜的力学特性，包括闩锁状态（横桥循环减少时的持续力）。该模型还预测，横桥磷酸化的ATP消耗大约等于横桥循环的ATP消耗，并且ATP消耗将随着稳态力的增加呈双曲线上升。这篇综述表明，这些预测与颈动脉中膜现有的能量学数据一致。共价调节的绝对能量成本适中，且低于与闩锁状态相关的能量节省。然而，相对于横纹肌，共价调节会降低平滑肌的总机械效率。
