title: Differential inhibition of platelet aggregation and calcium mobilization by nitroglycerin and stabilized nitric oxide.
abstract: We compared the mechanisms of the antiplatelet effects of nitroglycerin (NTG) and stabilized nitric oxide (NO). Stabilized NO was in the form of S-nitrosothiols [S-nitroso-albumin (S-NO-Alb) and S-nitrosocaptopril (S-NO-Cap)] or heme-NO [sodium nitro-prusside (SNP)]. The molecular structure of S-NO-Cap was confirmed by mass spectrometry. NTG, SNP, S-NO-Alb, and S-NO-Cap inhibited ADP-induced platelet aggregation dose dependently. The inhibitory IC50 value was 109 microM for NTG, 0.98 microM for SNP, 2.99 microM for S-NO-Alb, and 2.5 microM for S-NO-Cap. NTG (200 microM) released 15.4 microM nitrite anion into platelet-rich plasma (PRP) after 60-min incubation, to which platelets contributed 5.4 microM. On the other hand, SNP and S-NO-Cap released undetectable amounts of NO2- when incubated in either PRP or platelet-poor plasma (PPP). The platelet cytosolic calcium ion (Ca2+) concentration was measured fluorometrically in Fura-2-loaded gel-filtered platelets. Thrombin-induced Ca2+ mobilization was significantly inhibited by 10 microM NTG, SNP, S-NO-Alb, and S-NO-Cap, whereas resting Ca2+ was unaltered. Ca2+ mobilization was inhibited 28.6% by NTG, 91.9% by SNP, 90.0% by S-NO-Alb, and 92.7% by S-NO-Cap. These results demonstrate that NTG is an exogenous donor of NO, but releases it only slowly. On the other hand, SNP and S-nitrosothiols inhibited platelet aggregation by the action of stabilized NO incorporated in their structure and did not release NO. NTG and stabilized NO shared a common mechanism of antiplatelet activity, which involved inhibition of calcium mobilization.
authors.affiliation: First Department of Internal Medicine, Shiga University of Medical Science, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Amano
authors.forename: M
authors.initials: M
authors.lastname: Takahashi
authors.forename: T
authors.initials: T
authors.lastname: Kosaka
authors.forename: M
authors.initials: M
authors.lastname: Kinoshita
mesh_terms: D000328:Adult; D000368:Aged; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002216:Captopril / Q000031:analogs & derivatives / Q000138:chemical synthesis / Q000494:pharmacology; D005260:Female; D006801:Humans; D066298:In Vitro Techniques; D008297:Male; D008875:Middle Aged; D009569:Nitric Oxide / Q000494:pharmacology*; D005996:Nitroglycerin / Q000494:pharmacology*; D009603:Nitroso Compounds; D010974:Platelet Aggregation / Q000187:drug effects*; D010975:Platelet Aggregation Inhibitors / Q000494:pharmacology*; D012710:Serum Albumin, Bovine / Q000138:chemical synthesis / Q000494:pharmacology; D014665:Vasodilator Agents / Q000138:chemical synthesis / Q000494:pharmacology
chemical_list: D009603:Nitroso Compounds; D010975:Platelet Aggregation Inhibitors; C091665:S-nitrosoalbumin; D014665:Vasodilator Agents; C060039:S-nitrosocaptopril; D012710:Serum Albumin, Bovine; D009569:Nitric Oxide; D002216:Captopril; D005996:Nitroglycerin; D002118:Calcium