Inhibition of platelet aggregation by L-arginine and polyamines in alloxan treated rats

The antiaggregating effect of L-arginine and polyamines (putrescine, spermidine and spermine) was studied in platelets of normal and diabetic rats (120 mg/Kg alloxan, i.p.). This effect was compared with insulin. The assays of platelet aggregation were carried out using platelet-rich plasma (PRP) obtained from both groups of animals. The platelet aggregation test were first standardized by using PRP obtained from human health donors. 2.5 mumoles/ml ADP, 250 mumoles/ml epinephrine and 0.4 U/ml of thrombin were used as inductors of platelet aggregation. 60% of inhibition was observed with 10 microM of L-arginine or polyamines in PRP of normal rats, and 50% with PRP of diabetic rats when thrombin was used as an agonist. These results show that L-arginine and the polyamines putrescine, spermidine and spermine have an antagonist action in platelet aggregation. In addition, we demonstrated the platelet arginase activity not only in rat platelets but also in human, was less under hyperglycaemia. The activity of this enzyme has been associated with polyamine synthesis, required to regulate platelet function.