Human blood platelets lack nitric oxide synthase activity

Abstract

Reports on expression and functionality of nitric oxide synthase (NOS) activity in human blood platelets and erythrocytes are contradictory. We used a specific gas chromatography–mass spectrometry (GC–MS) method to detect NOS activity in human platelets. The method measures simultaneously [¹⁵N]nitrite and [¹⁵N]nitrate formed from oxidized ¹⁵N-labeled nitric oxide (¹⁵NO) upon its NOS-catalyzed formation from the substrate l-[guanidino-¹⁵N₂]-arginine. Using this GC–MS assay, we did not detect functional NOS in non-stimulated platelets and in intact platelets activated by various agonists (adenosine diphosphate, collagen, thrombin, or von Willebrand factor) or lysed platelets. l-[guanidino-nitro]-Arginine-inhibitable NOS activity was measured after addition of recombinant human endothelial NOS to lysed platelets. Previous and recent studies from our group challenge expression and functionality of NOS in human platelets and erythrocytes.

• Enzyme activity assays
• mass spectrometry
• nitric oxide
• stable isotopes

Declaration of interest

The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article. Financial support was granted to DT (TS 60/4-1) and SFB 688 (TP A2) to S. G. from the Deutsche Forschungsgemeinschaft (Germany).