S-transnitrosylation of albumin in human plasma and blood in vitro and in vivo in the rat

S-Nitrosoalbumin (SNOALB) is the most abundant physiological circulating ni tric oxide (NO) carrier regulating NO-dependent biological actions in human s. The mechanisms of its formation and biological actions are still incompl etely understood. Nitrosation by authentic NO and S-transnitrosylation of t he single sulfhydryl group located at Cys-34 of human albumin by the physio logical S-nitroso compounds S-nitrosocysteine (SNOC) and S-nitrosoglutathio ne (GSNO) are two possible mechanisms. On a quantitative basis, we investig ated by gas chromatography-mass spectrometry the contribution of these two mechanisms to SNOALB formation in human plasma and blood in vitro. GSNO and SNOC (0-100 muM) rapidly and efficiently (recovery = 35%) S-transnitrosyla ted albumin to form SNOALB. NO (100 muM) S-nitrosated albumin to SNOALB at a considerably lower extent (recovery = 50%). The putative NO-donating drug s glyceryl trinitrate and sodium nitroprusside teach 100 muM) failed comple tely in S-nitrosating albumin. Bubbling NO into human plasma and blood resu lted in formation of SNOALB that inhibited ADP-induced platelet aggregation . Infusion of GS(15)NO in the rat resulted in formation of S(15)NOALB, [N-1 5]nitrate and [[N-15]nitrite. Our results suggest that S-transnitrosylation of albumin by SNOC and GSNO could be a more favored mechanism for the form ation of SNOALB in the circulation in vivo than S-nitrosation of albumin by NO itself. (C) 2001 Elsevier Science B.V. All rights reserved.