THE EFFECT OF ACETYLSALICYLIC-ACID ON FIBRIN GEL LYSIS BY TISSUE-PLASMINOGEN ACTIVATOR

The in vitro effect of acetylsalicylic acid (ASA) on fibrin gel lysis by exogenous t-PA was studied in 13 patients with angina pectoris. Six patients received 75 mg, and seven patients 160 mg of ASA. Plasma clo ts were formed and lysed in microtiter plate wells and turbidity monit ored spectrophotometrically. Mean lysis times in the 75 mg group were 8.7, 11.4 and 11.2 min during ASA treatment, and after 1 and 2 weeks A SA withdrawal respectively. Reduced changes were observed in the 160 m g group. Additionally, a relationship was found between the fibrin fib er mass/length ratio, i.e. fiber thickness in mature clots and lysis t imes after ASA administration (P = 0.0015). Importantly, fibers are th icker during treatment with ASA. It was subsequently demonstrated that the potential to produce thicker fibers by varying the thrombin conce ntration has a noticeable effect on turbidimetric profiles in the pres ence of exogenous t-PA. This effect was similar to the changes observe d during and after ASA treatment. Thus, these results suggest that the enhancement of fibrin gel lysis during ASA treatment may be due to al terations in gel structure. In addition, a reduction in the fibrin mas s in lower turbidity clots, suggests an added mechanism by which ASA m ay enhance lysis.