Ueda S, Oiki S, Okada Y
J Membr Biol. 1986;91(1):65-72. doi: 10.1007/BF01870215.
Using Ca2+- and K+-selective microelectrodes, the cytosolic free Ca2+ and K+ concentrations were measured in mouse fibroblastic L cells. When the extracellular Ca2+ concentration exceeded several micromoles, spontaneous oscillations of the intracellular free Ca2+ concentration were observed in the submicromolar ranges. During the Ca2+ oscillations, the membrane potential was found to oscillate concomitantly. The peak of cyclic increases in the free Ca2+ level coincided in time with the peak of periodic hyperpolarizations. Both oscillations were abolished by reducing the extracellular Ca2+ concentration down to 10(-7) M or by applying a Ca2+ channel blocker, nifedipine (50 microM). In the presence of 0.5 mM quinine, an inhibitor of Ca2+-activated K+ channel, sizable Ca2+ oscillations still persisted, while the potential oscillations were markedly suppressed. Oscillations of the intracellular K+ concentration between about 145 and 140 mM were often associated with the potential oscillations. The minimum phase of the K+ concentration was always 5 to 6 sec behind the peak hyperpolarization. Thus, it is concluded that the oscillation of membrane potential results from oscillatory increases in the intracellular Ca2+ level, which, in turn, periodically stimulate Ca2+-activated K+ channels.
使用钙和钾选择性微电极，测定了小鼠成纤维细胞L细胞胞质内游离钙和钾的浓度。当细胞外钙浓度超过几微摩尔时，在亚微摩尔范围内观察到细胞内游离钙浓度的自发振荡。在钙振荡期间，发现膜电位随之振荡。游离钙水平周期性升高的峰值与周期性超极化的峰值在时间上一致。通过将细胞外钙浓度降低到10^(-7) M或应用钙通道阻滞剂硝苯地平（50微摩尔），两种振荡均被消除。在存在0.5毫摩尔奎宁（一种钙激活钾通道抑制剂）的情况下，相当大的钙振荡仍然持续，而电位振荡则被显著抑制。细胞内钾浓度在约145至140毫摩尔之间的振荡常与电位振荡相关。钾浓度的最低相位总是在超极化峰值后5至6秒。因此，可以得出结论，膜电位的振荡是由细胞内钙水平的振荡性升高引起的，而细胞内钙水平的升高又周期性地刺激钙激活钾通道。
