Halligan R D, Shelat H, Kahn A M
Department of Medicine, Medical School, University of Texas Health Science Center, Houston 77225.
Am J Physiol. 1991 Feb;260(2 Pt 1):C347-54. doi: 10.1152/ajpcell.1991.260.2.C347.
Intracellular pH (pHin) affects vascular smooth muscle function, but the mechanisms that control pHin in this tissue are not well understood. These studies were performed to determine whether sarcolemmal vesicles from bovine superior mesenteric artery (SMA) contain a Na(+)-independent Cl(-)-HCO3- exchanger and, if so, to determine its sensitivity to membrane voltage and inhibitors. 36Cl- was taken up by vesicles into an osmotically active intravesicular space. In Na(+)-free media, an outwardly or inwardly directed HCO3- gradient stimulated 36Cl- transport in the opposite direction. An outwardly directed unlabeled Cl- gradient stimulated 36Cl- uptake by a mechanism that was inhibited by external HCO3-. HCO3- or Cl- gradient-stimulated 36Cl- uptake was not due to voltage coupling between ions. In the nominal absence of HCO3-, a threefold outwardly directed OH- gradient did not affect 36Cl- uptake. Total 36Cl- uptake was stimulated by an inside-positive voltage, but the HCO3- gradient-stimulated component of 36Cl- uptake was insensitive to a change in membrane voltage. Finally, HCO3- gradient-stimulated 36Cl- uptake was inhibited by 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS) and furosemide, with 50% inhibitory concentration values equalling approximately 1.0 and 0.5 mM, respectively. These data indicate that sarcolemmal vesicles from bovine SMA contain a Na(+)-independent Cl(-)-HCO3- exchanger. This transport system is probably electroneutral and is inhibitable by DIDS and furosemide. A conductive pathway for Cl- is present in the vesicles, but Cl(-)-OH- exchange activity was not observed.
细胞内pH值（pHin）影响血管平滑肌功能，但该组织中控制pHin的机制尚未完全明确。进行这些研究是为了确定来自牛肠系膜上动脉（SMA）的肌膜囊泡是否含有不依赖Na⁺的Cl⁻-HCO₃⁻交换体，如果是，则确定其对膜电压和抑制剂的敏感性。³⁶Cl⁻被囊泡摄取到具有渗透活性的囊泡内空间。在无Na⁺的培养基中，外向或内向的HCO₃⁻梯度刺激³⁶Cl⁻向相反方向转运。外向的未标记Cl⁻梯度通过一种被外部HCO₃⁻抑制的机制刺激³⁶Cl⁻摄取。HCO₃⁻或Cl⁻梯度刺激的³⁶Cl⁻摄取不是由于离子之间的电压偶联。在名义上无HCO₃⁻的情况下，三倍外向的OH⁻梯度不影响³⁶Cl⁻摄取。总的³⁶Cl⁻摄取受到膜内正电压的刺激，但³⁶Cl⁻摄取的HCO₃⁻梯度刺激成分对膜电压变化不敏感。最后，HCO₃⁻梯度刺激的³⁶Cl⁻摄取被4,4'-二异硫氰基芪-2,2'-二磺酸（DIDS）和呋塞米抑制，50%抑制浓度值分别约为1.0和0.5 mM。这些数据表明，来自牛SMA的肌膜囊泡含有不依赖Na⁺的Cl⁻-HCO₃⁻交换体。该转运系统可能是电中性的，并且可被DIDS和呋塞米抑制。囊泡中存在Cl⁻的传导途径，但未观察到Cl⁻-OH⁻交换活性。
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