Antithrombotic effect of a polysaccharide fraction from Laminaria japonica from the South China Sea.

Some in vitro studies have identified an antithrombotic effect of polysaccharides from Laminaria japonica, but this activity remains to be confirmed in vivo. In this study a polysaccharide fraction termed PLG was extracted from L. japonica in the Beibu Gulf in Guangxi, China, and its antithrombotic effects explored in rat models of carotid and venous thrombosis. Its anticoagulation and antiplatelet properties were assessed by measuring the prothrombin time (PT), activated partial thromboplastin time (APTT) and ADP-induced platelet aggregation rate (Agg(max)). Its effects on bleeding time were measured using the tail transection method. It was found that pretreatment with an intraperitoneal injection of PLG at 2.5 or 5.0 mg/kg significantly prolonged the occlusion time in the carotid thrombosis model, and a dose of 5.0 mg/kg reduced the thrombus weight in the venous thrombosis model. Pretreatment with PLG (5.0 mg/kg) increased the APTT and decreased the ADP-induced platelet Agg(max). Neither dose of PLG significantly prolonged the bleeding time compared with the control group. In an in vitro anticoagulation assay using human plasma, PLG at 57.14, 28.57 and 28.57 μg/mL inhibited APTT and PT in a concentration-dependent manner. The results show that PLG possesses antithrombotic activity in a rat model, and that it may prove to be clinically useful in humans.