Aggregation of human blood platelets in the presence of the pyridoindole stobadine

The antiarrhythmic and cardioprotective drug stobadine, possessing antioxid ant and neuroprotective properties, was studied as to its in vitro effect o n aggregation of human blood platelets. Pretreatment of platelets with stob adine for 30 s inhibited stimulated platelet aggregation in a dose-dependen t way. Depending on the aggregation stimulus used, the minimal effective co ncentrations of the drug were 1 mu mol/l (adrenaline), 200 mu mol/l (ADP), and 1,000 mu mol/l (PMA). Aggregation induced with thrombin or Ca2+-ionopho re A23187 was not changed in the presence of stobadine even in the concentr ation of 1,000 mu mol/l. Addition of stobadine 30 s after adrenaline was al so effective and terminated aggregation (100 and 1,000 mu mol/l) or prolong ed onset of its second phase (10 mu mol/l). The presented experiments showe d stobadine as a potent inhibitor of adrenaline-induced aggregation, indica ting its involvement in the observed antithrombotic and cytoprotective acti vity.