Abstract

Polyphloretin phosphate (PPP) as well as its large and small molecular weight fractions were tested in two different experimental models with platelet aggregation and release. Platelet aggregation and release of mediators from platelets were induced in dogs by infusions of thrombin or protamine. Apart from lowering the platelet count, these substances also caused increased pulmonary arterial pressure, decreased systemic blood pressure and increased tracheal insufflation pressure. PPP, as well as its large molecular weight fraction, inhibited the fall of platelet count as well as hemodynamic and respiratory changes caused by thrombin and protamine. The small molecular weight fraction of PPP did not inhibit these effects. It is concluded that PPP, as well as its large molecular weight fraction, inhibit platelet aggregation induced by thrombin and protamine but they do not inhibit the action of thrombin upon fibrinogen.