Nonionic contrast agents produce thrombotic effect by inducing adhesion of leukocytes on human endothelium.

The expression of P-selectin was more upregulated following the exposure to nonionic low osmolar contrast agents than to ionic contrast agents. Exposure to nonionic contrast agents led to a marked adhesion of leukocytes to endothelial cells. Thrombomodulin activity of endothelial cells was decreased, and plasminogen activator inhibitor-1 (PAI-1) and tumor necrosis factor (TNF) alpha in the supernatant were increased when leukocyte adhesion occurred after exposure to nonionic contrast agents. Results suggest that the adhesion of leukocytes to the endothelium increases procoagulant activity.