Direct characterization of the Na+/H+ exchanger in human platelets

FEBS Letters

Devynck, M.A.¹  Astarie, C.¹  David-Dufilho, M.¹ 

[1] Department of Pharmacology, CNRS SDI 61670, Necker Medical School, 156 rue de Vaugirard, 75015 Paris, France

关键词: Na+/H+ exchanger;    pHi;    Human platelet;   

DOI  :  10.1016/0014-5793(90)80854-C

学科分类：生物化学/生物物理

来源: John Wiley & Sons Ltd.

【 摘 要 】

The kinetic properties of the Na⁺/H⁺ exchanger in human platelets were investigated by direct measurements of pH_i as detected with the fluorescent dye, BCECF. In acid-loaded cells, the antiporter displayed a hyperbolic dependence regarding external Na⁺ with an apparent K _m of 38 ± 4 mM (pH_o 7.2 at 25°C) whereas its pH_i-dependent activation between 7.3 to 6.4 did not obey a Michaelian model. External acidification from 7.7 to 6.5 decreased significantly the initial rate of Na⁺-dependent H⁺ efflux. The amiloride derivative, ethylisopropylamiloride blocked this exchanger and exerted a non-competitive inhibition with respect to Na⁺ _o (K _i = 17 nM). The cation selectivity of the external site of the antiporter was Na⁺ > Li⁺ > K⁺ and choline. These results indicate that the BCECF technique allows to evaluate the main features of the Na⁺/H⁺ exchanger in human platelets, which possesses kinetic properties similar to those reported in other cell types.

【 授权许可】

Unknown