Figure 2-. NO bioavailabilty and eNOS activity under normoxia and hypoxia.
NO generation in the vasculature under normoxic conditions occurs through activation of the eNOS enzyme involving L-arginine substrate conversion to L-citrulline plus NO. eNOS generation of NO under hypoxic conditions can become dysfunctional due to enzyme uncoupling and ROS formation. Alternative non-enzymatic generation of NO under hypoxia can occur through nitrite/nitrate reduction back to NO via different molecular pathways.