Evidence that ADP hydrolysis by human cells is related to thrombogenic potential1

Washed monolayer cultures of human cells provoke the platelet release reaction to an extent comparable to irreversible aggregation with the following frequencies: endothelial, 0.0; smooth muscle; 0.67; fibroblast, 0.31. The ability of each cell type to hydrolyze exogenous adenine nucleotides was also compared. Endothelial cells and fibroblasts readily hydrolyze ATP and ADP, but smooth muscle cells have very little ectonucleotidase activity. The kinetic data suggest that the ability of endothelial cells to degrade ADP may contribute to their non-thrombogenic nature.These observations suggest that vascular-type cells may retain some of their non-thrombogenic characteristics in culture and that this $\text{in vitro}$ system may serve as a model for studying contributions of each portion of the vessel wall to hemostasis and thrombosis.