White J F
Am J Physiol. 1976 Oct;231(4):1214-9. doi: 10.1152/ajplegacy.1976.231.4.1214.
Intracellular potassium activity (aKi) has been determined in absorptive cells lining the villi of isolated, stripped proximal segments of Amphiuma small intestine. With single-barreled liquid ion-exchanger microelectrodes aKi = 41.6 +/- 1.5 mM in normal chloride buffer; with double-barreled microelectrodes constructed by a new method aKi = 38.5 +/- 2.4 mM. Also, by the latter approach aKi = 41.1 +/- 2.1 mM in buffer in which potassium was elevated to 5 meq/liter and aKi = 44.2 +/- 1.3 mM in sulfate buffer with the same bath potassium concentration. Since the calculated potassium equilibrium potential exceeds the membrane potential this ion is accumulated by the intestinal absorptive cell. A major portion of cellular potassium is bound or compartmentalized since the intracellular potassium activity coefficient is very low. A layer exists near the villi in which the potassium activity exceeds that in the bath buffer solution.
已测定了钝口螈小肠分离、剥离的近端节段绒毛内衬吸收细胞内的钾活性（aKi）。使用单管液体离子交换微电极，在正常氯化物缓冲液中aKi = 41.6±1.5 mM；使用新方法构建的双管微电极，aKi = 38.5±2.4 mM。此外，通过后一种方法，在钾浓度升高至5 meq/升的缓冲液中aKi = 41.1±2.1 mM，在具有相同浴钾浓度的硫酸盐缓冲液中aKi = 44.2±1.3 mM。由于计算出的钾平衡电位超过膜电位，这种离子被肠道吸收细胞积累。由于细胞内钾活度系数非常低，细胞内的大部分钾是结合的或分隔存在的。在绒毛附近存在一层，其中钾活性超过浴缓冲溶液中的钾活性。
