DIRECT PROOF OF NITRIC-OXIDE FORMATION FROM A NITROVASODILATOR METABOLIZED BY ERYTHROCYTES

When N-15-isosorbide dinitrate was injected into rats, the venous blood showed a 2-line hyperfine structure in the electron spin resonance (ESR) spectra of NO hemoglobin (HbNO), proving generation of N-15-NO. When human blood was mixed with N-15-isosorbide dinitrate anaerobically, ESR spectra showed initially N-14-HbNO, which was then overwhelmed with the increased N-15-HbNO. With deoxygenation of the blood of another 4 male donors without addition of isosorbide dinitrate, two showed 14N-HbNO, but others did not, suggesting varied amount of NO-precursers, nitrosothiols, in human blood. Neither N-ethylmaleimide nor S-hexylglutathione, a glutathione-S-transferase inhibitor, inhibited the formation of HbNO in the hemolysate mixed anaerobically with isosorbide dinitrite. (C) 1994 Academic Press. Inc.