Meissner G, McKinley D
J Membr Biol. 1976 Dec 25;30(1):79-98. doi: 10.1007/BF01869661.
Permeability properties and the effects of a changed membrane potential on Ca2+ release of sarcoplasmic reticulum vesicles of rabbit skeletal muscle were investigated by Millipore filtration. The relative permeability of sarcoplasmic reticulum to solutes determined under conditions of isotope exchange at equilibrium and/or under conditions of net flow of solute and water into the vesicles was as follows: sucrose, Ca2+, Mn2+ less than gluconate-, choline+, Tris+ less than methanesulfonate- less than urea, glycerol, K+, Na+,Li+, Cl-. Transient membrane potentials were induced by rapidly changing the ionic environment of the vesicles. Knowledge of the relative permeation rates of the above ions allowed prediction of the direction and extent of membrane polarization. Osmotic effects in the polarization measurements due to the rapid influx of solute and water into the vesicles were minimized by using media containing a fast (K+ or Cl-) and a relatively slow (gluconate- or choline+) penetrating ion. 45Ca2+ efflux from vesicles derived from different parts of the sarcoplasmic reticulum structure was not appreciably changed when vesicles were made more positive inside (choline chloride leads to potassium gluconate) or more negative inside (potassium gluconate leads to choline chloride). These studies suggest that part or all of the ion-induced changes in sarcoplasmic reticulum membrane permeability, previously interpreted to indicate "depolarization" -induced Ca2+ release, may be due to osmotic effects.
采用微孔过滤法研究了兔骨骼肌肌浆网囊泡的通透性特性以及膜电位变化对其Ca2+释放的影响。在同位素交换平衡条件下和/或溶质与水向囊泡净流动的条件下测定的肌浆网对溶质的相对通透性如下：蔗糖、Ca2+、Mn2+小于葡萄糖酸盐-、胆碱+、Tris+小于甲磺酸盐-小于尿素、甘油、K+、Na+、Li+、Cl-。通过快速改变囊泡的离子环境诱导瞬时膜电位。了解上述离子的相对渗透速率有助于预测膜极化的方向和程度。通过使用含有快速（K+或Cl-）和相对缓慢（葡萄糖酸盐-或胆碱+）穿透离子的介质，可将溶质和水快速流入囊泡导致的极化测量中的渗透效应降至最低。当囊泡内部电位更正（氯化胆碱导致葡萄糖酸钾）或更负（葡萄糖酸钾导致氯化胆碱）时，来自肌浆网结构不同部位的囊泡的45Ca2+流出没有明显变化。这些研究表明，先前被解释为“去极化”诱导的Ca2+释放的部分或全部离子诱导的肌浆网膜通透性变化可能是由于渗透效应。
