Table 3.
NO Sources in the Vasculature
| Source | Location | O2condition to function |
|---|---|---|
| Hydroxylation of l-arginine by NOS1 | Nerve fibers; mast cells (45) | Sensitive to O2 (high Km) (30, 96) |
| Hydroxylation of l-arginine by NOS2 | Macrophages; aged endothelium; many tissues under inflammatory conditions (70, 84) | Sensitive to O2 (relatively high Km) (96) |
| Hydroxylation of l-arginine by NOS3 | Vascular endothelium; erythrocytes (51, 68) | Insensitive to O2 (low Km) (78) |
| Nitrite reduction by NOS3 | Endothelium (33) | NO released during anoxia (33) |
| mtNOS | Parenchymal tissues (55) | N/A |
| S-nitrosohemoglobin | Erythrocytes (64) | NO released during hypoxia (91) |
| S-nitroso-glutathione or S-nitrosoalbumin | Plasma (32) | NO released during hypoxia (32) |
| Nitrite reduction by hemoglobin | Erythrocytes, plasma (39) | NO released during hypoxia (39) |
| Nitrite reduction by myoglobin | Skeletal muscle and myocardial tissue (88) | NO released during hypoxia (88) |
| Nitrite reduction by xanthine oxidoreductase | Ischemic tissues (60, 62) | NO released under ischemic or anaerobic conditions (60, 62) |
| Nitrate and nitrite reductions by cytochrome | A variety of tissues (26, 59) | N/A |
| P450 reductase and cytochrome P450 |
Km refers to the Michaelis-Menten constant.