Nitrite represents an endocrine bioavailable storage pool of nitric oxide (NO•) that is bioactivated along the physiological oxygen gradient to regulate a number of vascular and cellular responses. In vivo, nitrite may be converted to NO• by several mechanisms including acidic disproportionation, and enzymatic conversion via xanthine-oxidoreductase (XOR), mitochondrial enzymes, deoxyhemoglobin, and deoxymyoglobin (deoxyMb).