Could thrombus age be a modulator of heparin or L.M.W.H. activities?

The main thrombotic diseases are caused by old constituted thrombi. However, experiments to demonstrate the effects of heparin or heparin fragments on tPA release have been on fresh thrombi. This study on thrombi induced 6, 24, 48 or 72 hours before sampling shows variations in the main biological activities of both heparin and heparin fragment (CY222) as the thrombus ages. This effect is particularly observed on tPA release which is statistically reduced (p less than 0.001). Thrombus age seems to be a modulator of heparin and heparin fragment biological activities.