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Arterioscler Thromb Vasc Biol. 2002 Dec 1;22(12):2003-9.

Depolarization of endothelial cells enhances platelet aggregation through oxidative inactivation of endothelial NTPDase.

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  • 1Institute of Physiology, München, Germany. fkroetz@lmu.de

Abstract

OBJECTIVE:

The objective of this study was to investigate whether depolarization of cultured endothelial cells (human umbilical vein endothelial cells, HUVECs) affects their ectonucleotidase activity through superoxide (O2-) production.

METHODS AND RESULTS:

Depolarization by the cation channel gramicidin (100 nmol/L) or tetrabutylammonium chloride (1 mmol/L) induced O2- release from HUVECs (n=4), which was decreased by superoxide dismutase (SOD, 500 U/mL). The activity of endothelial ectonucleotidases was assessed by the production of inorganic phosphate from ADP, which was decreased by chronic depolarization by 25% (n=6, P<0.05) and the amount of AMP derived from ADP in the presence of the 5'-nucleotidase inhibitor alpha,beta-methylene-5'-diphosphate (100 micromol/L). AMP was decreased by chronic depolarization from 0.54+/-0.16 to 0.39+/-0.11 micromol/min/mg protein (n=6, P<0.05). This was abolished in the continuous presence of SOD (n=6). NTPDase protein was predominantly expressed in HUVECs (n=4). Protein abundance, viability of cells, and apoptosis rates were not altered by depolarization (n=10). Only in the presence of depolarized HUVECs, but not with control cells or with HUVECs depolarized in the presence of SOD, did 5 micromol/L of ADP cause irreversible platelet aggregation. Increases in transmural pressure induced endothelial depolarization in intact hamster small arterioles.

CONCLUSIONS:

Depolarization causes the endothelial production of O2-, which inhibits the activity of endothelial ectonucleotidases. Increases in transmural pressure induce endothelial depolarization. In chronically hypertensive diseases, depolarization might favor platelet aggregation.

PMID:
12482826
[PubMed - indexed for MEDLINE]
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