Okada Y, Tsuchiya W, Inouye A
J Membr Biol. 1979 Jun 7;47(4):357-76. doi: 10.1007/BF01869744.
Effects of divalent cations on oscillations of membrane potentials (i.e., spontaneous repetitive hyperpolarizing responses) and on hyperpolarizing responses induced by electrical stimuli as well as on resting potentials were studied in large nondividing L cells. Deprivation of Ca2+ from the external medium inhibited these hyperpolarizing responses accompanying slight depolarization of the resting potential Sr2+ or Mn2+ applied to the external medium in place of Ca2+ was able to substitute for Ca2+ in the generation of hyperpolarizing responses, while Mg2+, Ba2+ or La3+ suppressed hyperpolarizing responses. The addition of A23187 to the bathing medium or intracellular injection of Ca2+, Sr2+, Mn2+ or La3+ induced membrane hyperpolarization. When the external Ca2+, Sr2+ or Mn2+ concentration was increased, the resting potential also hyperpolarized, in a saturating manner. The amplitude of maximum hyperpolarization produced by high external Ca2+ was of the same order of magnitude as those of hyperpolarizing responses and was dependent on the external K+ concentration. In the light of these experimental observations, it was deduced that the K+ conductance increase associated with the hyperpolarizing excitation is the result of an increase in the intracellular concentration of free Ca2+ mainly derived from the external solution.
在不分裂的大型L细胞中，研究了二价阳离子对膜电位振荡（即自发性重复超极化反应）、电刺激诱导的超极化反应以及静息电位的影响。从外部培养基中去除Ca2+会抑制这些超极化反应，同时静息电位会出现轻微去极化。用Sr2+或Mn2+代替Ca2+加入外部培养基能够替代Ca2+产生超极化反应，而Mg2+、Ba2+或La3+则会抑制超极化反应。向浴液中添加A23187或细胞内注射Ca2+、Sr2+、Mn2+或La3+会诱导膜超极化。当外部Ca2+、Sr2+或Mn2+浓度增加时，静息电位也会以饱和方式超极化。高外部Ca2+产生的最大超极化幅度与超极化反应的幅度处于同一数量级，并且依赖于外部K+浓度。根据这些实验观察结果推断，与超极化兴奋相关的K+电导增加是细胞内游离Ca2+浓度增加的结果，而细胞内游离Ca2+主要来源于外部溶液。
