用双管钠液离子交换微电极测量牛蛙细胞内钠活性。

The measurement of intracellular sodium activities in the bullfrog by means of double-barreled sodium liquid ion-exchanger microelectrodes.

作者信息

Kotera K, Satake N, Honda M, Fujimoto M

出版信息

Membr Biochem. 1979;2(3-4):323-38. doi: 10.3109/09687687909063870.

PMID:42004

Abstract

A double-barreled Na+-selective microelectrode was constructed with monensin as a liquid ion exchanger. The HCl-treated monensin was dissolved in a solvent (Corning 477317) at 10% (weight/weight). Internal reference solution of its ionic barrel was mixture of 0.49 M NaCl and 0.01 M KCl, the pH being adjusted to 3 with 0.1 M citrate-HCl buffer, whereas that of the PD barrel was 0.5 M KCl. Average slope and selectivity ratio (Na+/K+) tested on 10 different microelectrodes were -57.5 +/- 1.87 mV/P(Na) (SEM) and 6.7 +/- 0.44, respectively. The electrical resistance was an order of 10(10) ohm and the response time was less than 10 sec. Using this microelectrode, a free flow micropuncture experiment was carried out in the bullfrog kidney and the intracellular Na+ activity as well as the membrane PD was determined on the proximal tubular cell. Average value (+/- SEM, n = 15) for the intracellular Na+ and K+ was 20.7 +/- 1.56 mEq/L and 61.2 +/- 1.16 mEq/L, respectively, and -68.7 +/- 0.88 mV for the peritubular membrane PD. There was a significant negative correlation between Na+ and K+ activities within the cell, i.e., the lower the ionic activity of cellular Na+ was, the higher the cellular K+, and vice versa, the sum of these two being kept nearly constant. The above finding may be somehow related to the isosmosis in the reabsorptive process across the proximal tubular epithelium.

摘要

以莫能菌素作为液体离子交换剂构建了双管 Na⁺ 选择性微电极。经 HCl 处理的莫能菌素以 10%（重量/重量）溶解于一种溶剂（康宁 477317）中。其离子管的内部参比溶液是 0.49 M NaCl 和 0.01 M KCl 的混合物，用 0.1 M 柠檬酸 - HCl 缓冲液将 pH 调至 3，而 PD 管的内部参比溶液是 0.5 M KCl。在 10 个不同的微电极上测试的平均斜率和选择性比（Na⁺/K⁺）分别为 -57.5 ± 1.87 mV/P(Na)（标准误）和 6.7 ± 0.44。电阻为 10¹⁰ 欧姆量级，响应时间小于 10 秒。使用该微电极，在牛蛙肾脏中进行了自由流动微穿刺实验，并测定了近端肾小管细胞内的 Na⁺ 活性以及膜电位差。细胞内 Na⁺ 和 K⁺ 的平均值（±标准误，n = 15）分别为 20.7 ± 1.56 mEq/L 和 61.2 ± 1.16 mEq/L，肾小管周围膜电位差为 -68.7 ± 0.88 mV。细胞内 Na⁺ 和 K⁺ 活性之间存在显著的负相关，即细胞内 Na⁺ 的离子活性越低，细胞内 K⁺ 越高，反之亦然，二者之和几乎保持恒定。上述发现可能与近端肾小管上皮重吸收过程中的等渗现象存在某种关联。