Sulfate-bicarbonate exchange in brush-border membranes from rat renal cortex.
Sulfate-bicarbonate exchange in brush-border membranes from rat renal cortex.
复制标题
大鼠肾皮质刷状缘膜中的硫酸盐-碳酸氢盐交换。
DOI：
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发表时间：
1987
影响因子：
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通讯作者：
J. B. Pritchard
中科院分区：
文献类型：
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作者：
J. B. Pritchard
在无Na+的条件下，大鼠肾刷状缘膜(BBM)囊泡对SO4(2-)的吸收可以通过施加HCO3-梯度(进大于出)来驱动。 SO4(2-)吸收的初始速率被刺激10倍，峰值超调超过平衡吸收2-3倍。 Cl-、SCN-、NO3-、I-、OH-能够替代HCO3-。二价阴离子，包括 SO4(2-) 本身，作为抗衡离子的效果较差。类似地，在不存在 Na+ 的情况下，单价离子最有效地刺激 SO4(2-) 流出。 HCO3- -SO4(2-) 交换受到二磺酸二苯乙烯 [4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic Acid (SITS)、4,4'-diisothiocyanostilbene-2,2'-disulfonic Acid (DIDS)]、根皮素、Hg 和 S2O3(2-) 顺式抑制。 HCO3 驱动的 SO4(2-) 吸收是饱和的，SO4(2-) 的表观 Km 为 0.4 mM。同时施加Na+（流出大于流入）和HCO3-（流入大于流出）梯度产生了SO4(2-)吸收的近似附加刺激。 SITS 抑制了 HCO3- 驱动的 SO4(2-) 吸收成分，但不抑制 Na+ 驱动的成分。最后，通过施加大于 HCO3- 梯度的输出，可以减少 Na+ 驱动的 SO4(2-) 积累，条件加速交换驱动的 SO4(2-) 流出。这些发现表明在相同的 BBM 囊泡中存在单独的 Na+-SO4(2-) 共转运和 SO4(2-)-阴离子交换途径。
Under Na+-free conditions, SO4(2-) uptake by rat renal brush-border membrane (BBM) vesicles could be driven by imposition of a HCO3- gradient (in greater than out). The initial rate of SO4(2-) uptake was stimulated 10-fold, and peak overshoot exceeded equilibrium uptake by 2-3 times. Cl-, SCN-, NO3-, I-, and OH- were able to substitute for HCO3-. Divalent anions, including SO4(2-) itself, were less effective as counterions. Similarly, in the absence of Na+,SO4(2-) efflux was stimulated most effectively by the monovalent ions. HCO3- -SO4(2-) exchange was cis-inhibited by disulfonic stilbenes [4-acetamido-4'-isothiocyanostilbene-2,2'-disulfonic acid (SITS), 4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (DIDS)], phloretin, Hg, and S2O3(2-). HCO3- driven SO4(2-) uptake was saturable, with an apparent Km of 0.4 mM for SO4(2-). Simultaneous imposition of Na+ (out greater than in) and HCO3- (in greater than out) gradients produced approximately additive stimulation of SO4(2-) uptake. The HCO3- -driven component of SO4(2-) uptake, but not the component driven by Na+, was inhibited by SITS. Finally, Na+-driven SO4(2-) accumulation could be reduced by imposing an out greater than in HCO3- gradient, conditions accelerating exchange driven SO4(2-) efflux. These findings indicate the presence of separate Na+-SO4(2-) cotransport and SO4(2-)-anion exchange pathways in the same BBM vesicles.