Lamprecht G, Seidler U, Classen M
II. Department of Medicine, Technische Universität München, Germany.
Am J Physiol. 1993 Nov;265(5 Pt 1):G903-10. doi: 10.1152/ajpgi.1993.265.5.G903.
Na(+)-H+ and Cl(-)-base exchangers on the parietal cell have been demonstrated by several authors. Controversy exists concerning a basolateral Na(+)-HCO3- cotransporter in the parietal cell. To clarify this issue, we prepared highly enriched basolateral membrane (BLM) and apical-tubulovesicular membrane (to serve as negative controls) vesicles from rabbit fundic mucosa. Na(+)-H+ exchange was demonstrated by measuring pH gradient-driven amiloride-sensitive 22Na+ uptake and Na+ gradient-driven proton uptake into voltage-clamped BLM but not into apical-tubulovesicular vesicles. Anion exchange was demonstrated by measuring 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)-inhibitable influx of 36Cl- into Cl(-)- or HCO3(-)-loaded voltage-clamped BLM vesicles. Na(+)-HCO3- cotransport was assessed by comparing HCO3(-)-driven 22Na uptake with uptake driven by an identical pH gradient. No significant difference was found between 22Na uptake in the presence and absence of HCO3-; 1 mM amiloride inhibited 22Na uptake > 90% in both conditions, whereas 2 mM DIDS had no effect. In BLM vesicles prepared from rabbit renal cortex, however, a HCO3- gradient stimulated 22Na uptake much more than an equivalent pH gradient, and DIDS inhibited this HCO3- gradient-driven 22Na uptake. This indicates that our experimental setup was suitable to detect a Na(+)-HCO3- cotransporter if present. Our data suggest that the parietal cell BLM contains Na(+)-H+ exchangers and Cl(-)-HCO3- exchangers but no Na(+)-HCO3- cotransporter.
几位作者已证实壁细胞上存在Na(+)-H+和Cl(-)-碱交换体。关于壁细胞基底外侧Na(+)-HCO3-共转运体存在争议。为阐明这一问题，我们从兔胃底黏膜制备了高度富集的基底外侧膜（BLM）和顶端微管泡膜（作为阴性对照）囊泡。通过测量pH梯度驱动的氨氯地平敏感的22Na+摄取以及Na+梯度驱动的质子摄取进入电压钳制的BLM来证实Na(+)-H+交换，但未在顶端微管泡囊泡中检测到。通过测量4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS）抑制的36Cl-流入Cl(-)-或HCO3(-)-负载的电压钳制的BLM囊泡来证实阴离子交换。通过比较HCO3(-)驱动的22Na摄取与相同pH梯度驱动的摄取来评估Na(+)-HCO3-共转运。在有和没有HCO3-存在的情况下，22Na摄取未发现显著差异；1 mM氨氯地平在两种情况下均抑制22Na摄取>90%，而2 mM DIDS没有作用。然而，在从兔肾皮质制备的BLM囊泡中，HCO3-梯度刺激的22Na摄取比等效的pH梯度刺激得多，并且DIDS抑制这种HCO3-梯度驱动的22Na摄取。这表明我们的实验设置适合检测如果存在的Na(+)-HCO3-共转运体。我们的数据表明壁细胞BLM含有Na(+)-H+交换体和Cl(-)-HCO3-交换体，但不含有Na(+)-HCO3-共转运体。
