Identification of nitric oxide (NO) in human blood.

The amount of nitric oxide (NO) in the blood of residents of urban and suburban areas was measured under steady-state conditions by isotopic dilution with N15O, followed by field-ionization mass spectrometry. Approximately 20 nmoles of NO per ml of blood was characteristic of both smokers and nonsmokers, except for one of the eight subjects who had a significantly lower level. Monkeys (Macaca speciosa) had values comparable to those of seven human subjects, and rats had values like that of the unique human subject. Whether the origin of the NO was endogenous or exogenous was not determined.