Cell shape change and cytosolic Ca2+ in human umbilical-vein endothelial cells stimulated with thrombin

We quantified thrombin-induced endothelial cells shape change and investigated the role of Ca2+ in such shape change. We used the fluorescent Ca2+ indicator, fura2, to measure both shape change as cell size and intracellular free Ca2+ ([Ca2+]i), in cultured human umbilical-vein endothelial cells (HUVEC). Thrombin induced concentration-dependent decreases in cell size (percentage of cell size at 6 min after stimulation with 0.01 U/ml, 0.1 U/ml, or 1 U/ml thrombin) was 90.1 +/- 1.5%, 78.1 +/- 2.4%, and 40.9 +/- 2.4%, respectively. Thrombin also increased [Ca2+]i in a concentration-dependent manner. Both depletion of extracellular Ca2+, and also the addition of W5, a calmodulin antagonist, inhibited thrombin-induced size reduction. These results indicate an association between shape change and [Ca2+]i mobilization in human endothelial cells stimulated by thrombin.