N-ACETYLCYSTEINE POTENTIATES NITROGLYCERIN-INDUCED REVERSAL OF PLATELET-AGGREGATION

N-Acetylcysteine (N-AC) potentiates the systemic and coronary hemodyna mic and antianginal effects of nitroglycerin (NGT) in humans; NTG/N-AC reduces the incidence of acute myocardial infarction in patients with unstable angina pectoris. Although previous studies have demonstrated that NTG exerts antiaggregatory effects on platelets, little informat ion is available concerning the possible potentiation by N-AC of NTG a ntiplatelet effects. In the present study, we examined the in vitro ef fects of NTG and the combination of NTG with N-AC on reversal of ADP-i nduced aggregation in platelet-rich plasma (PRP) obtained from normal subjects and patients with stable angina pectoris. We also examined th e potential effect of background aspirin therapy on this interaction. NTG, added to platelets 0.5 min after the beginning of aggregation, su ppressed the incipient aggregation and provoked the appearance of a di saggregation phase, resulting in a concentration-dependent reversal of platelet aggregation. Platelet responsiveness to NTG was significantl y less (p < 0.01) in both groups of patients (receiving and not receiv ing aspirin) as compared with normal subjects. N-AC (10(-5) M), which did not in itself affect aggregation, induced a threefold potentiation (p < 0.05) of the antiaggregating effect of NTG that was similar in d egree for all tested groups of individuals. This potentiation of the a ntiplatelet effects of NTG by N-AC may contribute to the efficacy of c ombined NTG/N-AC therapy in patients with acute ischemic syndromes.