Platelet Ca2+ Homeostasis: Na+-Ca2+ Exchange in Plasma Membrane Vesicles
- 1 January 1987
- journal article
- research article
- Published by Georg Thieme Verlag KG in Thrombosis and Haemostasis
- Vol. 57 (03) , 337-340
- https://doi.org/10.1055/s-0038-1651129
Abstract
A vesicular plasma membrane-enriched fraction obtained from human platelets exhibited 45Ca2+ uptake in exchange for intravesicular Na+. The rate of Ca2+ uptake was linear up to 4 sec. The apparent Km for Ca2+ was 22 pM and the Vmax 280 pmol/mg/ sec. Ca2+ efflux from Ca2+ loaded vesicles was obtained upon dilution into a NaCl but not a KC1 medium. The extent of Ca2+uptake was monotonically increased as the pH increased from 6 to 9. Na+-Ca2+ exchange was shown to be electrogenic. Ca2+ uptake was distinguished from binding by the induction of Ca2+ release after A23187 addition. These findings support a role for Na+-Ca2+ exchange in human platelet Ca2+ transport.Keywords
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