Kinetics of Cl-dependent K fluxes in hyposmotically swollen low K sheep erythrocytes.
Kinetics of Cl-dependent K fluxes in hyposmotically swollen low K sheep erythrocytes.
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DOI：
10.1085/jgp.97.2.173
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发表时间：
1991-02
期刊：
影响因子：
--
通讯作者：
Lauf PK
中科院分区：
文献类型：
--
作者：
Delpire E;Lauf PK
在低氧肿胀的低钾羊红细胞中进行了K:Cl共运输的详细动力学研究，以表征外向载体的性质。通过制霉菌素法改变细胞K和不同细胞外K或Rb浓度的红细胞在零K反式条件下的K外排和K内流速率测定动力学参数。虽然外流和内流的表观亲和力非常相似，但K外流的最大速度大约是内流的两倍。此外，在热力学平衡时（即当电池内的K和Cl离子积等于电池外的离子积时），观察到与温度相关的净K流出，只有当外部产物达到内部产物的大约两倍时才接近零。离子与转运体的结合顺序是不对称的，外部是有序的（先结合Cl，后结合K），内部是随机的。KCl反式抑制钾的外排而非内流。用K外排的反式抑制来验证外部结合的顺序：在没有外部K的情况下，外部Cl会发生反式抑制，反之则不会。因此，在低氧肿胀的低钾羊红细胞中，K:Cl共转运是动力学不对称的。
A detailed kinetic study of K:Cl cotransport in hyposmotically swollen low K sheep red blood cells was carried out to characterize the nature of the outwardly poised carrier. The kinetic parameters were determined from the rate of K efflux and influx under zero-K-trans conditions in red cells with cellular K altered by the nystatin method and with different extracellular K or Rb concentrations. Although apparent affinities for efflux and influx were quite similar, the maximal velocity for K efflux was approximately two times greater than for influx. Furthermore, at thermodynamic equilibrium (i.e., when the ion product of K and Cl within the cell was equal to that outside) a temperature-dependent net K efflux was observed, approaching zero only when the external product reached approximately two times the internal product. The binding order of the ions to the transporter was asymmetric, being ordered outside (Cl binding first, followed by K) and random inside. K efflux but not influx was trans-inhibited by KCl. Trans inhibition of K efflux was used to verify the order of binding outside: trans inhibition by external Cl occurred in the absence of external K, but not vice versa. Thus K:Cl cotransport is kinetically asymmetric in hyposmotically swollen low K sheep red cells.