Physiopathologic effects of nitric oxide and its relationship with oxi
dative stress. Nitric oxide (NO .) is produced from L-arginine, as res
ult of a reaction catalyzed by the enzyme nitric oxide synthase (NOS).
The reaction is the sole source of NO . in animal tissues. NO . can c
ontrol physiological processes (or systems) such as (a) blood pressure
; (b) relaxation of arterial smooth muscle; (c) platelet aggregation a
nd adhesion; (d) neurotransmission; (e) neuroendocrine secretion. NO .
contributes to the killing of patogenic microorganisms and tumoral ce
lls by phagocytes. NO . reacts with superoxide anion thus producing pe
roxynitrite, a cytotoxic ion capable of destroying many biological tar
gets. The superoxide/peroxinitrite balance determines the ONOO- produc
tion and, accordingly, is essential for the development of hypertensio
n, atheroesclerosis, neurodegenerative diseases, viral infections, isc
hemia-reperfusion injury, and cancer.