thromboxane-b2 and rhyncophylline

Rhynchophylline (Rhy) inhibited rabbit platelet aggregation induced by arachidonic acid (AA), collagen, and ADP. The values of IC50 were 0.72, 0.74, and 0.67 mmol.L-1, respectively. Rhy reduced the thromboxane B2 (TXB2) generation in PRP induced by collagen but failed to reduce that induced by AA. Rhy suppressed malondialdehyde (MDA) formation in platelet suspension stimulated by thrombin, inhibited the platelet factor 4 (PF4) release. It did not alter intraplatelet cAMP concentration. Rhy 10-20 mg.kg-1 iv showed a significant inhibition of venous thrombosis and cerebral thrombosis in rats.

Topics: Alkaloids; Animals; Cyclic AMP; Indole Alkaloids; Intracranial Embolism and Thrombosis; Male; Malondialdehyde; Oxindoles; Platelet Aggregation; Platelet Aggregation Inhibitors; Platelet Factor 4; Rabbits; Rats; Rats, Inbred Strains; Thrombophlebitis; Thromboxane B2

Rhyncophylline (Rhy) produced a potent inhibition of rat platelet aggregation in ex vivo. TXA2 generation in platelet rich plasma from rats treated with Rhy obviously decreased in the collagen-induced group, but was not altered in the AA-induced group. These results suggest that Rhy suppressed the release of AA from platelet phospholipids stimulated by collagen, and this may be one of the mechanisms related to its action on platelet aggregation. Pretreatment with ASA, but not Rhy, reduced plasma PGI2 in rats. In the in vitro system, the PGI2 synthesis in rat aorta was shown to be inhibited by ASA but was not by Rhy. Rhy significantly reduced the number of mice died due to thrombosis by platelet aggregates. ASA prevented collagen plus adrenaline induced thrombotic death while Rhy prevented both ADP and collagen plus adrenaline induced thrombotic death.

Topics: 6-Ketoprostaglandin F1 alpha; Alkaloids; Animals; Drugs, Chinese Herbal; Indole Alkaloids; Oxindoles; Platelet Aggregation; Platelet Aggregation Inhibitors; Rats; Rats, Inbred Strains; Thrombosis; Thromboxane B2