Gillespie J I
J Physiol. 1983 Nov;344:359-77. doi: 10.1113/jphysiol.1983.sp014945.
The free ion concentrations of Na+, K+ and Cl- have been measured in the cells and intercellular spaces of developing amphibian embryos using ion-sensitive microelectrodes. Ca2+, H+ and buffering capacity have also been measured in the intercellular spaces. The free intracellular Na+ and K+ concentrations in the early cleavage stages remain approximately constant at 21 mM and 90 mM respectively. The free intracellular Cl- concentration, approximately 60 mM during the egg to 4-cell stage, falls during development to around 30 mM by the 128-cell stage. Embryos from different batches show a wide variation in intracellular free ion content. A strong correlation was observed between the ion content, particularly of K+, and the viability of the embryo. If the intracellular K+ concentration was less than 60 mM, embryos invariably died between late blastula and early gastrula stages; if greater than 80 mM the embryo generally survived. The intercellular free Na+, K+, Cl- and Ca2+ concentrations in Xenopus mid-blastula embryos are 91 mM, 4 mM, 59 mM and 1.5 mM respectively. The intercellular potential at late neurula stages is +3.5 mV when the embryo is bathed in 5% Ringer solution; changing to Ringer solution reduced the potential to -4 mV. Before gastrulation the intercellular Ca2+ concentration in Xenopus falls to approximately 0.5 mM, where it remains throughout gastrulation before returning to its mid-blastula value during neurulation. In Xenopus, the intercellular Na+ concentration falls to around 75 mM and the intercellular K+ concentration rises to around 17 mM at the end of gastrulation. These changes are not maintained and both Na+ and K+ concentrations return to their earlier values. In Ambystoma, the intercellular K+ concentration falls steadily from 7 mM at the mid-blastula stage to 2 mM at the end of neurulation. The Na+ concentration is constant at approximately 93 mM up to stage 14; between stages 14 and 16 the measurements show some scatter (minimum value 60 mM, maximum value 100 mM), and beyond stage 16 the Na+ concentration increases to 123 mM.
利用离子敏感微电极测量了发育中的两栖类胚胎细胞和细胞间隙中Na⁺、K⁺和Cl⁻的游离离子浓度。还测量了细胞间隙中的Ca²⁺、H⁺和缓冲能力。早期卵裂阶段细胞内游离Na⁺和K⁺浓度分别保持在约21 mM和90 mM左右。细胞内游离Cl⁻浓度在卵到4细胞阶段约为60 mM，在发育过程中到128细胞阶段降至约30 mM。不同批次的胚胎细胞内游离离子含量差异很大。观察到离子含量，尤其是K⁺含量与胚胎活力之间存在很强的相关性。如果细胞内K⁺浓度低于60 mM，胚胎在囊胚后期和原肠胚早期之间总是死亡；如果高于80 mM，胚胎通常存活。非洲爪蟾囊胚中期胚胎细胞间游离Na⁺、K⁺、Cl⁻和Ca²⁺浓度分别为91 mM、4 mM、59 mM和1.5 mM。当胚胎浸泡在5%林格氏液中时，神经胚后期的细胞间电位为+3.5 mV；换成林格氏液后电位降至-4 mV。在原肠胚形成之前，非洲爪蟾细胞间Ca²⁺浓度降至约0.5 mM，在整个原肠胚形成过程中保持在该水平，直到神经胚形成期间恢复到囊胚中期的值。在非洲爪蟾中，原肠胚形成结束时细胞间Na⁺浓度降至约75 mM，细胞间K⁺浓度升至约17 mM。这些变化并未持续，Na⁺和K⁺浓度都恢复到早期值。在美西螈中，细胞间K⁺浓度从囊胚中期的7 mM稳步下降到神经胚形成结束时的2 mM。直到第14阶段，Na⁺浓度一直稳定在约93 mM；在第14阶段和第16阶段之间，测量结果显示有些分散（最小值60 mM，最大值100 mM），超过第16阶段后，Na⁺浓度增加到123 mM。
