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. Author manuscript; available in PMC: 2021 Jan 1.
Published in final edited form as: Nitric Oxide. 2019 Oct 8;94:1–8. doi: 10.1016/j.niox.2019.10.005

Figure 7. Schematic representation of nitrate/nitrite/NO pathways in human skeletal muscle cells explored in this study.

Figure 7.

Dietary nitrate and, to a lesser extent, nitrite, are presumably transported into the human skeletal muscle cell by anion transporters, such as sialin and the chloride channel 1 (CLC1). Nitrate is also produced during the “futile” cycle of NOS1. Inside the cell, nitrate can be reduced into nitrite by xanthine oxidoreductase (XOR), which is a known mammalian nitrate reductase. Other molybdenum-containing proteins, mitochondrial amidoxime-reducing component (MARC-1 and MARC-2) and aldehyde oxidase (AO), are also expressed in these cells and might potentially play a role in reducing nitrate into nitrite and nitrite into NO. NO is also produced during productive cycle of NOS1. NO acts on soluble guanylyl cyclase (sGC), which produces cyclic GMP (cGMP), the downstream messenger of nitric oxide. This scheme shows only the part of the nitrate/nitrite/NO cycle directly connected with the present study. Other known pathways (not shown on the scheme), are the reduction of nitrite to NO by deoxymyoglobin and oxidation of nitrite and NO into nitrate by oxymyoglobin.