In vitro-inhibition of shear-induced platelet aggregation by verapamil

The purpose of the study was to investigate the effect of verapamil on shear induced platelet aggregation (SIPA). Blood of New Zealand rabbit was collected to prepare platelet-rich-plasma (PRP) by routine centrifugation. A cone-plate shear device was employed to generate shear stress. The verapamil-treated PRP or control PRP were sheared at 37 degrees C for 120 sec. SIPA was determined from counting of free platelet. The inhibition rates of SIPA by verapamil for five doses at three shear levels were calculated accordingly. The concentration of half inhibition (IC50) was 0.03, 0.07 and 0.09 mmol/l for 20, 40 and 52 dyn/cm2, respectively. The regression for IC50 of verapamil and shear stress follows the linear equation: IC50=-0.0071+0.0019tau (r=0.999,P=0.03). The results indicate that calcium antagonist may have the potential for inhibition of SIPA although the current IC50 for rabbit platelet is higher than that of human routine blood concentration of verapamil.