FIBRINOLYSIS AND SEROTONIN UNDER CYCLOSPORINE-A TREATMENT IN RENAL-TRANSPLANT RECIPIENTS

Cyclosporine A (CyA), a potent immnosuppressive drug, has been used in renal transplant recipients with increasing frequency since 1982. Despite its efficacy, CyA therapy has been associated with an increased incidence of thromboembolic complications (1). This has been attributed to increased thromboxane production (2), reduced prostacyclin synthesis and increased platelet aggregability (3,4). The coagulation system is also altered in CyA-treated patients and some of these changes would favor thrombosis (1). Increased fibrinogen and FVIII:C levels have also been associated with an enhanced risk of thrombosis (1). In contrast, CyA therapy was reported to increase the levels of antithrombin III and protein C (1), two proteins known to protect against venous thromboembolism. However, the possible effect of CyA on the fibrinolytic system has not been thoroughly investigated and rather confusing data have been reported concerning both enhancement (5) and suppression of fibrinolysis (6). Serotonin (5-hydroxytryptamine, 5-HT) may play a role in hemostasis (7) and platelet/vessel wall interactions (8). It may facilitate platelet thrombus formation by potentiating the aggregatory response to other agents such as ADP, collagen or epinephrine and by causing vasoconstriction. Taking all these data into consideration we have measured some fibrinolytic parameters, whole blood and plasma serotonin concentration in cyclosporine A- and non-cyclosporine A-treated kidney transplant recipients.