Best P M, Abramcheck C W
Biophys J. 1985 Dec;48(6):907-13. doi: 10.1016/S0006-3495(85)83853-4.
The efflux of 42K from single, skinned (sarcolemma removed) skeletal muscle fibers has been determined. Isotope washout curves are kinetically complex and can be fit as the sum of three exponentials, including a fast component (k = 0.25 s-1) with a pool size equivalent to 91% of the fiber volume, an intermediate component (k = 0.08 s-1) equivalent to 6% of the fiber volume, and a slow component (k = 0.008 s-1) equivalent to 0.5% of fiber volume. Only the intermediate kinetic component is significantly affected by pretreatment of fibers with detergent. Efflux curves from detergent-treated fibers could be fit as the sum of two exponentials with coefficients and rate constants comparable to those of the fast and slow component of washout of untreated controls. Similarly the washout of [14C]sucrose can be described as the sum of two exponentials. We conclude that the intermediate component of 42K washout results from the movement of ions from a membrane bound space within the skinned fiber. Because of its relative volume, the sarcoplasmic reticulum seems to be a reasonable choice as a structural correlate for this component. Our estimate of the potassium permeability for the sarcoplasmic reticulum (SR) based on the efflux data is 10(-7) cm/s. This value is less than previous estimates from isolated preparations.
已测定了单个剥除肌膜（肌膜去除）的骨骼肌纤维中42K的外流情况。同位素洗脱曲线在动力学上较为复杂，可拟合为三个指数之和，包括一个快速成分（k = 0.25 s-1），其池大小相当于纤维体积的91%，一个中间成分（k = 0.08 s-1）相当于纤维体积的6%，以及一个缓慢成分（k = 0.008 s-1）相当于纤维体积的0.5%。只有中间动力学成分受到用去污剂预处理纤维的显著影响。来自去污剂处理纤维的外流曲线可拟合为两个指数之和，其系数和速率常数与未处理对照洗脱的快速和缓慢成分相当。同样，[14C]蔗糖的洗脱也可描述为两个指数之和。我们得出结论，42K洗脱的中间成分是由于离子从剥除肌膜纤维内的膜结合空间移动所致。由于其相对体积，肌浆网似乎是该成分合理的结构相关物选择。基于外流数据，我们对肌浆网（SR）钾通透性的估计为10（-7）cm/s。该值小于先前从分离制剂得到的估计值。
