In vitro platelet adhesion to endothelial cells at low shear rates during copper deficiency in rats

Abstract

Dietary copper restriction impairs thrombogenesis and hemostasis in rat microcirculation. In this study, the role of wall shear rate in platelet-to-endothelial cell adhesion in vitro was studied during copper deficiency. Platelets were obtained from male, weanling Sprague-Dawley rats fed purified diets, which were either copper-adequate (CuA, 6.3 μg Cu/g) or copper-deficient (CuD, 0.3 μg Cu/g), for 4 weeks. Platelets were through a parallel plate flow chamber containing cultured rat endothelial cells which were either normal or treated with the copper chelator tetraethylenepentamine (TEPA). Since platelet von Willebrand factor (vWF) concentration is decreased in CuD rats, we determined the platelet adhesion when CuD platelets were incubated in purified vWF (0.2 units/ml). Adhesion to normal endothelial cells was significantly lower for CuD platelets vs. CuA platelets at low (70 s−1; 21.5 ± 4.0% vs. 37.0 ± 2.7%) and relatively high (200 s−1; 9.3 ± 1.7% vs. 19.5 ± 1.1%) wall shear rates. Adhesion of CuD platelets to normal endothelial cells incubated in vWF was not different from adhesion of CuA platelets. Adhesion to TEPA-treated endothelial cells was lower than adhesion to normal endothelial cells for both CuA and CuD platelets (30.6 ± 1.5% vs. 37 ± 2.7%). Although increasing the shear rate (from 70 s−1 to 200 s−1) decreased adhesion of both CuA and CuD platelets, the ratio between groups remained similar. These results demonstrate that adhesion of CuD platelets to normal endothelial cells is less than that of CuA platelets under flow conditions typical for venules. Further, altered shear rate does not account for the depressed in vitro platelet adhesion. Thus, alteration of platelet and endothelial cell properties by copper deficiency may be of greater importance than the effect of flow conditions on endothelial cells in delaying thrombosis. J. Trace Elem. Exp. Med. 12:25–36, 1999. Published 1999 Wiley-Liss, Inc.