Thromb Haemost 1987; 57(03): 337-340
DOI: 10.1055/s-0038-1651129
Original Article
Schattauer GmbH Stuttgart

Platelet Ca2+ Homeostasis: Na+-Ca2+ Exchange in Plasma Membrane Vesicles

Appavoo Rengasamy
The Department of Pharmacology University of Illinois College of Medicine at Chicago, Chicago, IL, USA
,
Soudabeh Soura
The Department of Pharmacology University of Illinois College of Medicine at Chicago, Chicago, IL, USA
,
Harold Feinberg
The Department of Pharmacology University of Illinois College of Medicine at Chicago, Chicago, IL, USA
› Author Affiliations
Further Information

Publication History

Received 02 October 1986

Accepted after revision 26 February 1987

Publication Date:
06 July 2018 (online)

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Summary

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.