title: Novel role for low molecular weight plasma thiols in nitric oxide-mediated control of platelet function.
abstract: 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 microm) 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 microm), cysteinyl-glycine (10 microm), or cysteine (10 microm). This NO-mediated effect was not seen with LMW thiols in the absence of albumin and was associated with S-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.
authors.affiliation: Centre for Cardiovascular Science, University of Edinburgh, United Kingdom.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Crane
authors.forename: Richard
authors.initials: R
authors.lastname: Ollosson
authors.forename: Kevin P
authors.initials: KP
authors.lastname: Moore
authors.forename: Adriano G
authors.initials: AG
authors.lastname: Rossi
authors.forename: Ian L
authors.initials: IL
authors.lastname: Megson
mesh_terms: D000367:Age Factors; D001792:Blood Platelets / Q000378:metabolism*; D003545:Cysteine / Q000737:chemistry; D004151:Dipeptides / Q000737:chemistry; D005978:Glutathione / Q000737:chemistry; D006454:Hemoglobins / Q000737:chemistry; D006801:Humans; D008956:Models, Chemical; D009569:Nitric Oxide / Q000737:chemistry / Q000378:metabolism*; D010974:Platelet Aggregation; D026403:S-Nitrosothiols / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013696:Temperature; D013997:Time Factors
chemical_list: D004151:Dipeptides; D006454:Hemoglobins; D026403:S-Nitrosothiols; D013438:Sulfhydryl Compounds; D009569:Nitric Oxide; C028505:cysteinylglycine; D005978:Glutathione; D003545:Cysteine