Anti-aggregatory actions of calcium channel blockers in cat platelets.

Four calcium channel blockers, verapamil, nifedipine, nisoldipine and nimodipine were studied in terms of their ability to inhibit platelet aggregation in cat platelet rich plasma by optical aggregometry. Only verapamil and nisoldipine significantly inhibited aggregation in cat platelets to ADP (2 microM). None of the calcium channel blockers exerted marked inhibition of aggregation induced by 1mM arachidonic acid. However, verapamil produced a moderate but significant inhibition of aggregation to arachidonic acid. Increasing the calcium ion concentration could reverse this inhibition. Thus, there are significant differences in the anti-aggregatory activity of calcium channel blockers in cat platelet rich plasma.