Depolarization of Endothelial Cells Enhances Platelet Aggregation Through Oxidative Inactivation of Endothelial NTPDase

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 (O ₂ ⁻ ) production. Methods and Results— Depolarization by the cation channel gramicidin (100 nmol/L) or tetrabutylammonium chloride (1 mmol/L) induced O ₂ ⁻ 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 P Conclusions— Depolarization causes the endothelial production of O ₂ ⁻ , which inhibits the activity of endothelial ectonucleotidases. Increases in transmural pressure induce endothelial depolarization. In chronically hypertensive diseases, depolarization might favor platelet aggregation.