Nitric oxide (NO) is a powerful antiplatelet agent, but its notoriously short biological half-life limits its potential to prevent the activation of circulating platelets. Here we used diethylamine diazeniumdiolate (DEA/NO) as an NO generator to determine whether the antiplatelet effects of NO are prolonged by the formation of a durable, plasma-borne S-nitrosothiol reservoir. Preincubation of both platelet rich plasma (PRP) and washed platelets (WP) with DEA/NO (2 μm) for 1 min inhibited collagen-induced platelet aggregation by 82 ± 5 and 91 ± 2%, respectively. After 30 min preincubation with DEA/NO, NO was no longer detectable in either preparation, but aggregation remained markedly inhibited (72 ± 7%) in PRP. In contrast, the inhibitory effect in WP was almost completely lost at this time (5 ± 3%) but was partially restored (39 ± 10%) in WP containing human serum albumin (1%) and fully restored by co-incubation with albumin and the low molecular weight (LMW) thiols, glutathione, (5 μm), cysteinyl-glycine (10 μm), or cysteine (10 μm). This NO-mediated effect was not seen with LMW thiols in the absence of albumin and was associated withS-nitrosothiol formation. Our results demonstrate that LMW thiols play an important role in both the formation and activation of an S-nitrosoalbumin reservoir that significantly prolongs the duration of action of NO.
This work was funded by British Heart Foundation FS/2001060 (to M. S. C.).The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
