Objective: 

Though melatonin is a hormone with multiple biological effects, its particular role in hemostasis is not yet thoroughly elucidated. The present study has been designed to provide screening data of the effects of melatonin on the basic integral parameters of hemostasis: prothrombin time (PT), activated partial thromboplastin time (APTT), thrombin time (TT) and euglobulin clot lysis time (ECLT) in rats.

Methods: 

The studies were performed on 26 male Wistar rats exposed to 12/12 h natural light/dark cycle. Thirteen rats were treated with Melatonin in a daily dose 0.2 mg/kg body mass applied twice daily s.c. for three days. The rest of the animals (control group) were treated with the vehicle by the same scheme and volume. The parameters tested were determined using standard laboratory kinetic tests on a Stago analyzer.

Results: 

PT, APTT, and TT were significantly shortened (p<0.001), while ECLT was elongated (p<0.001) by melatonin application.

Conclusions: 

The results indicate that melatonin inflicts substantial shifts in hemostasis by activating coagulation via both intrinsic and extrinsic pathways, and additionally enhances transformation of fibrinogen to fibrin. The elongated ECLT may be interpreted as an effect of the hormone on plasma plasminogen activators. The data suggest melatonin is involved in hemostasis regulation by generating a tendency of hypercoagulability and reduced plasma fibrinolytic activity.