Horres C R, Aiton J F, Lieberman M
Am J Physiol. 1979 Mar;236(3):C163-70. doi: 10.1152/ajpcell.1979.236.3.C163.
The relationship between the external potassium concentration ([K]o) and membrane permeability has been reexamined using a tissue-cultured preparation of embryonic chick heart cells in which diffusional limitations are minimal. The unidirectional K efflux and electrochemical gradients were determined as a function of [K]o, and the results showed that potassium permeability was constant within the range of 1-20 mM [K]o. Membrane potentials were obtained in K-free solutions and correlated with 42K efflux and intracellular ion content measurements under the same conditions. In contrast to preparations of the intact embryonic chick heart, 42K efflux does not decrease in K-free media. Simulations of tracer measurements at reduced [K]o from naturally occurring cardiac muscle indicate that the experimentally observed decrease in 42K efflux could result from diffusional limitations. This observation, when coupled with the experimental results, suggests that the effect of low [K]o on membrane permeability in homeothermic preparations of cardac muscle should be reevaluated.
利用胚胎鸡心脏细胞的组织培养制剂，重新研究了细胞外钾浓度（[K]o）与膜通透性之间的关系，在该制剂中扩散限制最小。测定了单向钾外流和电化学梯度作为[K]o的函数，结果表明，在1-20 mM [K]o范围内，钾通透性是恒定的。在无钾溶液中获得膜电位，并与相同条件下的42K外流和细胞内离子含量测量结果相关。与完整胚胎鸡心脏的制剂不同，在无钾培养基中42K外流不会减少。从天然心肌在降低的[K]o下对示踪剂测量的模拟表明，实验观察到的42K外流减少可能是由扩散限制导致的。这一观察结果与实验结果相结合，表明应重新评估低[K]o对恒温动物心肌制剂中膜通透性的影响。
