Shimada H, Burckhardt G
Pflugers Arch. 1986;407 Suppl 2:S160-7. doi: 10.1007/BF00584946.
The kinetics of sulfate uptake were studied in basolateral membrane vesicles from rat renal cortex. Sulfate uptake exhibits a DIDS-sensitive, saturable component, and a DIDS-insensitive component, which does not saturate in the tested sulfate concentration range (up to 10 mM). Intravesicular (= trans) sulfate strongly stimulates sulfate uptake by increasing Jmax and--to a lesser degree--by decreasing apparent Km. The marked dependence of Jmax on trans-sulfate indicates that the transport system operates as an anion exchanger. Half-maximal sulfate uptake occurs at 0.08-0.14 mmol/l extravesicular sulfate. Half-maximal trans-stimulation is observed at 11 mmol/l intravesicular sulfate indicating that the sulfate transporter is highly asymmetric. Lowering extravesicular pH stimulates sulfate uptake, suggesting that external protons are essential for sulfate uptake. This stimulation is mainly due to a decrease in Km. An inside positive membrane potential stimulates sulfate uptake at pHout = 8.8, but not at pHout = 6.4. These results are compatible with electrogenic sulfate transport at higher and electroneutral 2H+ -SO4(2-) cotransport at lower pH.
对来自大鼠肾皮质的基底外侧膜囊泡中硫酸盐摄取的动力学进行了研究。硫酸盐摄取表现出一种对4,4'-二异硫氰酸二苯乙烯-2,2'-二磺酸（DIDS）敏感的、可饱和的成分，以及一种对DIDS不敏感的成分，该成分在测试的硫酸盐浓度范围（高达10 mM）内不饱和。囊泡内（即反式）硫酸盐通过增加最大转运速率（Jmax）并在较小程度上通过降低表观米氏常数（Km）来强烈刺激硫酸盐摄取。Jmax对反式硫酸盐的显著依赖性表明该转运系统作为一种阴离子交换器发挥作用。在细胞外硫酸盐浓度为0.08 - 0.14 mmol/l时发生半数最大硫酸盐摄取。在囊泡内硫酸盐浓度为11 mmol/l时观察到半数最大反式刺激，表明硫酸盐转运体高度不对称。降低细胞外pH值会刺激硫酸盐摄取，这表明外部质子对于硫酸盐摄取至关重要。这种刺激主要是由于Km的降低。在细胞外pH值为8.8时，膜内正电位会刺激硫酸盐摄取，但在细胞外pH值为6.4时则不会。这些结果与较高pH值时的电生硫酸盐转运以及较低pH值时的电中性2H⁺ - SO₄²⁻共转运相一致。
