Figure 2.

eNOS uncoupling. Excess superoxide (O₂ ^•−) production, for example, after myocardial infarction, results in scavenging of nitric oxide (NO) to form peroxinitrite. The latter inhibits coupling of not only endothelial derived nitric oxide synthetase (eNOS) and tetrahydrobiopterin (BH₄), but also L-arginine and superoxide dismutase (SOD), which creates a downward spiral of enhanced O₂ ^•− production. Finally, eNOS gets uncoupled and produces O₂ ^•− rather than NO, sustaining the loop of nitroso-redox imbalance.