Influence of thiofedrine on platelet aggregation, intraplatelet cyclic cAMP and malondialdehyde in rats.

Platelet aggregation and cyclic adenosine monophosphate (cAMP) production were studied by turbidimetry and competitive protein binding assay, respectively, in rats. Thiofedrine (Thi) significantly inhibited adenosine diphosphate (ADP)-induced and thrombin-induced platelet aggregation in vitro, with IC50 values of 0.56 and 0.16 mmol/l, respectively. In vivo, Thi 1.25-5.0 mg/kg i.v. significantly inhibited ADP-induced platelet aggregation at rate of 17.1-40.3%. Thi caused a dose-dependent increase in cAMP levels in rat washed platelets. Malondialdehyde (MDA) levels in rat platelets were measured by colorimetry. Thi had an inhibitory effect on thrombin-induced platelet MDA production. The results suggest that the antiaggregatory action of Thi may be related to metabolism of arachidonic acid (AA) and elevation of cAMP levels.