Figure 7. Circulating nitrite serves as an alternative nitric oxide donor only in the presence of deoxyHb and/or deoxyMb .

A, rhythmic handgrip exercise significantly increases skeletal muscle deoxyHb and deoxyMb content, as measured by NIR over the flexor digitorum profundus muscle (n = 6). Insert: original NIR record, showing a steep increase in deoxyHb content during the transition from rest to exercise. All data are expressed as a percentage of the TLS. B, sodium nitrate significantly increases circulating plasma nitrite concentration in patients with BMD (n = 6). C, circulating NO₂ ⁻is reduced to NO via deoxyHb in the microvascular space, and by deoxyMb in skeletal myocytes, leading to improvements in skeletal muscle blood flow regulation. Data are reported as the mean + SE.