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Direct characterization of the Na + /H + exchanger in human platelets
Author(s) -
Astarie C.,
David-Dufilho M.,
Devynck M.A.
Publication year - 1990
Publication title -
febs letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.593
H-Index - 257
eISSN - 1873-3468
pISSN - 0014-5793
DOI - 10.1016/0014-5793(90)80854-c
Subject(s) - sodium–hydrogen antiporter , antiporter , chemistry , amiloride , efflux , biophysics , selectivity , sodium , nuclear chemistry , membrane , biochemistry , biology , catalysis , organic chemistry
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.