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

The purpose of the study was to investigate the effect of verapamil on shea r induced platelet aggregation (SIPA). Blood of New Zealand rabbit was coll ected to prepare platelet-rich-plasma (PRP) by routine centrifugation. A co ne-plate shear device was employed to generate shear stress. The verapamil- treated PRP or control PRP were sheared at 37 degreesC for 120 sec. SIPA wa s determined from counting of free platelet. The inhibition rates of SIPA b y verapamil for five doses at three shear levels were calculated accordingl y. The concentration of half inhibition (IC50) was 0.03, 0.07 and 0.09 mmol /l for 20, 40 and 52 dyn/cm(2), respectively. The regression for IC50 of ve rapamil and shear stress follows the linear equation: IC50 = -0.0071 + 0.00 19 tau (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 o f verapamil.