Evidence suggests that citrulline plasmatic levels would be lower in several states involving systemic inflammation and hypoxia. Indeed, it has been observed in rats that hypoxia leads to a sharp decline in plasma CIT concentration and also in human (hypocitrullinemia has been observed in Intensive Care Unit patients and in subjects suffering from sepsis and trauma) but the cause of relationship is not yet established. Therefore, it may be supposed that a decreased plasma CIT level could be responsible for a decrease in de novo ARG synthesis leading to an impairment of NO production (endothelial dysfunction) in these pathological situations.