Cremaschi D, Meyer G, Bottà G, Rossetti C
Dipartimento di Fisiologia e Biochimica Generali, Università di Milano, Italy.
Pflugers Arch. 1988 Nov;413(1):102-4. doi: 10.1007/BF00581237.
The transapical Cl- influx and transepithelial Na+ transport were measured in rabbit gallbladder. Only 11.7% of the transported Na+ was found to be accompanied by HCO3-. 10(-4) M SITS eliminated the HCO3- dependent fraction of Cl- influx (50%) but did not significantly alter intracellular Na+ activity and Na+ transport. Exposure to HCO3-free salines or to 10(-4) M acetazolamide about halved Cl- influx and Na+ transport. 25 mM SCN- reduced Cl- influx to zero, decreased intracellular Na+ activity, but only halved Na+ transport which under these conditions was abolished only in the absence of HCO3-. Exposure to a Cl- -free saline produced effects similar to those caused by SCN-. These results suggest that when Cl-/HCO3- exchange is inhibited at the apical membrane, Na+/H+ exchange and transepithelial Na+ transfer are unmodified if HCO3- is available for transport. The permanent uncoupling of the exchangers and the elevated transepithelial transport of Na+ are not due to an increased activity of the parallel Na+-Cl- cotransport but to a redirection of HCO3- flux toward the basolateral side.
在兔胆囊中测量经心尖的Cl⁻内流和跨上皮Na⁺转运。发现仅有11.7%被转运的Na⁺伴有HCO₃⁻。10⁻⁴M的SITS消除了Cl⁻内流中依赖HCO₃⁻的部分（50%），但并未显著改变细胞内Na⁺活性和Na⁺转运。暴露于无HCO₃⁻的盐溶液或10⁻⁴M乙酰唑胺中，Cl⁻内流和Na⁺转运约减半。25mM的SCN⁻使Cl⁻内流降至零，降低了细胞内Na⁺活性，但仅使Na⁺转运减半，在这些条件下，只有在无HCO₃⁻时Na⁺转运才被完全消除。暴露于无Cl⁻的盐溶液产生的效应与SCN⁻引起的效应相似。这些结果表明，当顶端膜处的Cl⁻/HCO₃⁻交换被抑制时，如果有HCO₃⁻可供转运，Na⁺/H⁺交换和跨上皮Na⁺转运不受影响。交换体的永久解偶联和Na⁺跨上皮转运的增加并非由于平行的Na⁺-Cl⁻协同转运活性增加，而是由于HCO₃⁻通量重新导向基底外侧。
