琥珀酸跨兔肾刷状缘膜转运的电生理学研究
Electrophysiology of succinate transport across rabbit renal brush border membranes.
作者信息
Schell R E, Wright E M
出版信息
J Physiol. 1985 Mar;360:95-104. doi: 10.1113/jphysiol.1985.sp015605.
In rabbit renal brush border membrane vesicles, the membrane potential was monitored using a voltage-sensitive optical probe (diS-C3-(5)). The ionic dependence of the electrogenic Na+/succinate co-transporter was determined in the presence of monovalent anions and mono-, di-, and trivalent cations. Na+ and La3+ were the only cations capable of supporting a succinate-dependent membrane depolarization: Li+, K+, Rb+, Cs+, NH4+, Hg2+, Ca2+, Ba2+, Sr2+, Mg2+, Cu2+, Fe2+, Cd2+, Be2+, Pb2+, Zn2+, Mn2+ and Co2+ did not. Succinate increased the Na+ permeability of the brush border membrane in a saturable manner: saturating succinate (3 mM) concentrations increased the Na+/K+ permeability (PNa/PK) ratio from 0.6 to 2.3. In the presence of Na+, Li+ and Hg2+ inhibit the succinate potential: cis-Li+ inhibition is competitive with an apparent Ki of 2 mM, while trans-Li+ is noncompetitive; cis-Hg2+ decreased the maximal depolarization with an inhibitor constant Ki of 8 microM, and this effect was irreversible. Cations having no effect included K+, Rb+, Cs+, NH4+, Ba2+, Ca2+, Mg2+, Sr2+, Cu2+, Fe2+, Cd2+, Co2+, Be2+, Zn2+, Pb2+, Mn2+, and La3+. It is concluded that succinate/Na+ co-transport produces a specific increase in the Na+ conductance of renal brush borders.
在兔肾刷状缘膜囊泡中，使用电压敏感光学探针（diS-C3-(5)）监测膜电位。在一价阴离子以及一价、二价和三价阳离子存在的情况下，测定了电生性Na⁺/琥珀酸共转运体的离子依赖性。Na⁺和La³⁺是仅有的能够支持琥珀酸依赖性膜去极化的阳离子：Li⁺、K⁺、Rb⁺、Cs⁺、NH₄⁺、Hg²⁺、Ca²⁺、Ba²⁺、Sr²⁺、Mg²⁺、Cu²⁺、Fe²⁺、Cd²⁺、Be²⁺、Pb²⁺、Zn²⁺、Mn²⁺和Co²⁺则不能。琥珀酸以可饱和的方式增加刷状缘膜的Na⁺通透性：饱和的琥珀酸（3 mM）浓度可使Na⁺/K⁺通透性（PNa/PK）比值从0.6增加到2.3。在有Na⁺存在的情况下，Li⁺和Hg²⁺抑制琥珀酸电位：顺式Li⁺的抑制作用具有竞争性，表观Ki为2 mM，而反式Li⁺是非竞争性的；顺式Hg²⁺使最大去极化降低，抑制剂常数Ki为8 μM，且这种作用是不可逆的。无作用的阳离子包括K⁺、Rb⁺、Cs⁺、NH₄⁺、Ba²⁺、Ca²⁺、Mg²⁺、Sr²⁺、Cu²⁺、Fe²⁺、Cd²⁺、Co²⁺、Be²⁺、Zn²⁺、Pb²⁺、Mn²⁺和La³⁺。得出的结论是，琥珀酸/Na⁺共转运使肾刷状缘的Na⁺电导率产生特异性增加。
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