Consumption of nitrogen oxide species at baseline, during NO synthase
inhibition, and during exercise with NO synthase inhibition. Arterial
and venous nitrite and S-nitrosothiol gradients were
multiplied by flow measurements to determine consumption (positive
value on the y axis) or, in the case of HMW-SNO,
production (negative value on the y axis). SNO-Hb: Basal
SNO-Hb consumption was 92 ± 86 pmol/ml/min/100 ml of
tissue. SNO-Hb consumption increased nonsignificantly from 143 ±
83 pmol/ml/min/100 ml of tissue during L-NMMA infusion to
366 ± 471 pmol/ml/min/100 ml of tissue during L-NMMA
infusion with exercise. Data are expressed as the mean ± SEM.
HMW-SNO: At baseline, HMW-SNO forms (negative value for consumption) in
the peripheral circulation at a rate of 23 ± 14
pmol/ml/min/100 ml of tissue. Although there was no significant
change in the formation of HMW-SNO during L-NMMA infusion (25 ± 8
pmol/ml/min/100 ml of tissue), a trend toward increased formation
of HMW-SNO was observed during exercise and L-NMMA infusion (127
± 117 pmol/ml/min/100 ml of tissue). Nitrite: Nitrite
consumption significantly increased with exercise, from 156 ± 59
pmol/ml/min/100 ml of tissue during L-NMMA infusion to 1583
± 517 pmol/ml/min/100 ml of tissue during L-NMMA infusion with
exercise, suggesting that intravascular nitrite is used even during
physiological stress.