Analysis of urinary nitric oxide metabolites in healthy subjects

Nitric oxide (NO) has divergent actions under physiological and pathologica l conditions. NO is rapidly decomposed to nitrite (NO2-) and nitrate (NO3-) . Since these metabolites are stable, they are good indices of NO productio n under various conditions. In the present study, we measured NO2- and NO3- concentrations in the urine collected from 62 hospital controls and 504 he althy subjects by means of a new HPLC system combined with Griess reaction. NOx was the sum of NO2- and NO3-. There was no considerable inter-day vari ation in urinary NO metabolite levels, and there was close correlation betw een NO2-, NO3- and NOx values in spot urine obtained in the early morning a nd those in 24-h stored urine in hospital controls. Urinary NO metabolite l evels, which were corrected by creatinine (Cr) excretion and expressed on a logarithmic scale, showed normal distribution and were independent of sex and age in healthy subjects. The normal ranges of urinary NO2-, NO3- and NO x levels were estimated as 17-72 mu mol/g Cr, 1,023-2,818 mu mol/g Cr, and 1,071-2,951 mu mol/g Cr, respectively. We also found that urinary NO metabo lite levels were lower than normal range in patients with various diseases.