Increased CD54 and CD106 mRNA steady-state levels in thrombin-activated HUVECs. PCR products of RNA prepared from HUVECs stimulated by 8 U/mL of thrombin for different times were deposited on a 2% agarose gel. ICAM-1 mRNA was detected in unstimulated cells but increased after 2 hours and remained high after 24 hours of thrombin stimulation. VCAM-1 mRNA was detected in unstimulated HUVECs, raised to a maximum level between 4 and 6 hours and then decreased until 24 hours.