Cremaschi D, Hénin S, Meyer G
J Membr Biol. 1979 May 21;47(2):145-70. doi: 10.1007/BF01876114.
Bicarbonate presence in the bathing media doubles Na+ and fluid transepithelial transport and in parallel significantly increases Na+ and Cl- intracellular concentrations and contents, decreases K+ cell concentration without changing its amount, and causes a large cell swelling. Na+ and Cl- lumen-to-cell influxes are significantly enhanced, Na+ more so than Cl-. The stimulation does not raise any immediate change in luminal membrane potential and cannot be due to a HCO3(-)-ATPase in the brush border. The stimulation goes together with a large increase in a Na+-dependent H+ secretion into the lumen. All of these data suggests that HCO3- both activates Na+--Cl- cotransport and H+--Na+ countertransport at the luminal barrier. Thiocyanate inhibits Na+ and fluid transepithelial transport without affecting H+ secretion and HCO3(-)-dependent Na+ influx. It reduces Na+ and Cl- conentrations and contents, increases the same parameters for K+, causes a cell shrinking, and abolishes the lumen-to-cell Cl- influx. It enters the cell and is accumulated in the cytoplasm with a process which is Na+-dependent and HCO3(-)-activated. Thus SCN- is likely to compete for the Cl- site on the cotransport carrier and to be slowly transferred by the cotransport system itself.
在浴液介质中存在碳酸氢盐会使钠离子和液体的跨上皮转运增加一倍，同时显著提高细胞内钠离子和氯离子的浓度及含量，降低钾离子的细胞内浓度但不改变其总量，并导致细胞大幅肿胀。钠离子和氯离子从管腔到细胞的内流显著增强，钠离子的增强程度超过氯离子。这种刺激不会立即引起管腔膜电位的变化，且不可能归因于刷状缘中的碳酸氢根 -ATP 酶。这种刺激伴随着向管腔内钠离子依赖性氢离子分泌的大幅增加。所有这些数据表明，碳酸氢根在管腔屏障处既激活钠离子 - 氯离子共转运，也激活氢离子 - 钠离子逆向转运。硫氰酸盐抑制钠离子和液体的跨上皮转运，而不影响氢离子分泌和依赖碳酸氢根的钠离子内流。它降低钠离子和氯离子的浓度及含量，增加钾离子的相同参数，导致细胞收缩，并消除从管腔到细胞的氯离子内流。它进入细胞并在细胞质中积累，这一过程是钠离子依赖性的且由碳酸氢根激活。因此，硫氰根可能会竞争共转运载体上的氯离子位点，并由共转运系统自身缓慢转运。
