Amlodipine,Nitric Oxide,and Platelet Aggregation

Abstract

This study examined the effect of a single dose of 0.4 mg·kg⁻¹ amlodipine on platelet aggregation with and without the nitric oxide synthase inhibitor, Nw-nitro-L-arginine. Blood samples were collected from rhesus monkeys at 0, 1, 2, and 6 hours after administration of amlodipine. Aggregation in platelet-rich plasma was stimulated by 10 μM adenosine diphosphate, 20 μM epinephrine, or 2 μg·mL⁻¹ collagen. Administration of Nw-nitro-L-arginine alone significantly increased platelet aggregation for up to 2 hours. This effect was antagonized by amlodipine administered 30 minutes after Nw-nitro-L-arginine. The findings suggest that in platelet-rich plasma, the inhibition of platelet aggregation by amlodipine might be mediated by nitric oxide, a potent endogenous inhibitor of aggregation.