Requirement for Ca2+ signaling in the mechanism of thrombin-induced increase in endothelial permeability. Sandoval, Raudel, Asrar B. Malik, Tabassum Naqvi, Dolly Mehta, and Chinnaswamy Tiruppathi. Department of Pharmacology, College of Medicine, The University of Illinois at Chicago, Chicago, Illinois 60612
APStracts 7:0261L, 2000.
We compared the thrombin-activated responses in human umbilical vein endothelial cells (HUVECs) and a HUVEC-derived cell line, ECV304. Thrombin induced a 40-50% decrease in transendothelial monolayer electrical resistance and a twofold increase in 125I-albumin permeability in HUVECs, whereas it failed to alter the endothelial barrier function in ECV304 cells. Thrombin produced a brisk intracellular Ca2+ concentration transient and phosphorylation of 20-kDa myosin light chain in HUVECs but not in ECV304 cells. Thrombin-induced phosphoinositide hydrolysis was comparable in ECV304 cells and HUVECs, indicating the activation of thrombin receptors in both cell types. La3+ reduced both the thrombin-induced decrease in endothelial monolayer electrical resistance and the increase in 125I-albumin permeability in HUVECs. Because the absence of Ca2+ signaling could explain the impairment in the permeability response in ECV304 cells, we studied the effect of increasing intracellular Ca2+ concentration in ECV304 cells with thapsigargin. Exposure of ECV304 cells to thapsigargin caused decreased endothelial monolayer electrical resistance and increased 125I-albumin permeability. These results indicate that Ca2+ influx and activation of Ca2+-dependent signaling pathways are important determinants of the thrombin-induced increase in endothelial permeability. 

Received 18 July 2000; accepted in final form 30 August 2000
APS Manuscript Number L242-0.
Article publication pending Am J Physiol Lung Cell Mol Physiol
ISSN 1080-4757 Copyright 2000 The American Physiological Society.
Published in APStracts on 30 November 2000