HCO3- transport in basolateral membrane vesicles isolated from rat renal cortex.
HCO3- transport in basolateral membrane vesicles isolated from rat renal cortex.
复制标题
从大鼠肾皮质分离的基底外侧膜囊泡中的 HCO3- 转运。
DOI：
10.1016/s0021-9258(18)61561-3
复制
发表时间：
1987
期刊：
影响因子：
--
通讯作者：
C. Ross
中科院分区：
文献类型：
--
作者：
S. Grassl;P. Holohan;C. Ross
采用大鼠肾皮质分离膜泡检测Na+-HCO3-共转运，探讨HCO3-跨近端小管基底外膜转运的机制。22Na+摄取表明，施加向内的HCO3-浓度梯度会诱导囊内Na+的短暂浓度积累。在没有HCO3-的情况下，只有施加羟基梯度才能刺激基底侧膜泡Na+摄取，因此对基底侧膜泡Na+摄取的刺激是特异性依赖于HCO3（-）的。刷状膜囊泡中未检测到Na+- hco3 -共转运的证据。在没有其他驱动力的情况下，囊泡内部的正电荷通过HCO3（-）依赖途径刺激囊泡内净Na+积累，这表明负电荷的流动伴随着Na+-HCO3-共转运事件。在阴离子转运抑制剂中，4-4′-二异硫氰二苯乙烯-2,2′-二磺酸在1 mM处表现出最强的抑制作用。Na+偶联转运抑制剂harmaline也能显著抑制HCO3-梯度驱动的Na+内流。通过适度抑制乙酰唑胺引起的HCO3梯度驱动的Na+内流，提示碳酸酐酶在Na+-HCO3-共转运机制中的作用。Cl-浓度梯度的施加对HCO3-梯度驱动的Na+内流有显著影响，这是速泻剂敏感的，符合Na+-HCO3-交换Cl-机制的操作。本研究结果为大鼠肾皮质基底外侧膜囊中存在电致Na+- hco3 -共转运蛋白而非微绒毛膜囊提供了证据。可能存在另一种基底侧膜HCO3（-）转运途径，介导Na+-HCO3-进行Cl-交换。
The mechanism of HCO3- translocation across the proximal tubule basolateral membrane was investigated by testing for Na+-HCO3- cotransport using isolated membrane vesicles purified from rat renal cortex. As indicated by 22Na+ uptake, imposing an inwardly directed HCO3- concentration gradient induced the transient concentrative accumulation of intravesicular Na+. The stimulation of basolateral membrane vesicle Na+ uptake was specifically HCO3(-)-dependent as only basolateral membrane-independent Na+ uptake was stimulated by an imposed hydroxyl gradient in the absence of HCO3-. No evidence for Na+-HCO3- cotransport was detected in brush border membrane vesicles. Charging the vesicle interior positive stimulated net intravesicular Na+ accumulation in the absence of other driving forces via a HCO3(-)-dependent pathway indicating the flow of negative charge accompanies the Na+-HCO3- cotransport event. Among the anion transport inhibitors tested, 4-4'-diisothiocyanostilbene-2,2'-disulfonic acid demonstrated the strongest inhibitor potency at 1 mM. The Na+-coupled transport inhibitor harmaline also markedly inhibited HCO3- gradient-driven Na+ influx. A role for carbonic anhydrase in the mechanism of Na+-HCO3- cotransport is suggested by the modest inhibition of HCO3- gradient driven Na+ influx caused by acetazolamide. The imposition of Cl- concentration gradients had a marked effect on HCO3- gradient-driven Na+ influx which was furosemide-sensitive and consistent with the operation of a Na+-HCO3- for Cl- exchange mechanism. The results of this study provide evidence for an electrogenic Na+-HCO3- cotransporter in basolateral but not microvillar membrane vesicles isolated from rat kidney cortex. The possible existence of an additional basolateral membrane HCO3(-)-translocating pathway mediating Na+-HCO3- for Cl- exchange is suggested.