Nitric oxide hemoglobin in patients receiving nitroglycerin as detected by electron paramagnetic resonance spectroscopy.

Blood specimens were obtained from 30 adult patients admitted to a coronary care unit after the decision to use nitroglycerin had been made by their physicians. The samples were drawn before nitroglycerin administration, within 1 hour after starting nitroglycerin, after several hours of therapy, and more than 4 hours after discontinuing therapy. One patient was admitted twice, accounting for 31 sets of blood specimens. A positive identification of nitric oxide-hemoglobin (NOHb), with electron paramagnetic resonance (EPR) spectroscopy could be made in the blood of 10 of the subjects after they had been receiving nitroglycerin for several hours (third blood sample). In seven subjects this third blood sample was not drawn, and they were dropped from the study. A final positive finding of NOHb was made in 10 of 24 patients. NOHb has not been identified previously in human subjects given nitroglycerin, and a significant dose-response relationship was observed between nitroglycerin and NOHb. We ascribe our inability to detect NOHb in all subjects before nitroglycerin (basal levels) and after nitroglycerin in 14 subjects to concentrations that were below the limits of detection of the technique as used. Subtraction of the EPR signal for plasma ceruloplasmin was necessary to detect the NOHb EPR signals. Thus we have shown EPR spectroscopy to be a highly specific and sensitive method for detecting and quantifying NOHb in human subjects. Further refinements in the technique to improve sensitivity are possible.(ABSTRACT TRUNCATED AT 250 WORDS)