Fig. 1
(Source: Allen et al. [52]. (Reproduced with permission from J.D Allen))
Nitrate–nitrite–nitric oxide formation/recycle pathways. In the presence of oxygen, endothelial nitric oxide synthase (NOS) catalyzes the oxidation l-arginine to nitric oxide (NO). NO is oxidized to nitrite (\( {\text{NO}}_{2}^{ - } \)) and nitrate (\( {\text{NO}}_{3}^{ - } \)). Dietary intake of inorganic nitrate (leafy green vegetables, beetroot) has been shown to increase plasma nitrate, which is concentrated in saliva where is it is reduced to nitrite by commensal oral bacteria. Nitrite can then be absorbed and further reduced to NO via several mechanisms, under hypoxic conditions. The pools of circulating nitrate and nitrite are subject to renal excretion, but are also able to be recycled back to NO [52]