Affiliations: Department of Pediatrics, Obstetrics and Gynecology,
University of Valencia, Valencia, Spain | Department of Pediatrics, Dr. Peset University
Hospital, Valencia, Spain
Note: [] Corresponding author: Ana Belén López-Jaén, Department of
Pediatrics, Obstetrics and Gynecology, University of Valencia, Avenida Blasco
Ibáñez, 15, 46010 Valencia, Spain. Tel.: +34 96 3864170; Fax: +34 96
3864815; E-mail: ana.belen.lopez@uv.es
Abstract: Reactive oxygen species (ROS) and reactive nitrogen species (RNS)
are normally produced in aerobic organisms. Free radicals play a physiological
role being necessary for cellular functioning because redox reactions are the
basis for numerous biochemical pathways as well as cellular chemistry,
biosynthesis of macromolecules and metabolic regulation. They can able to act
as second messengers, producing the stimulation of cell proliferation and being
mediators for the activation of cells. However, ROS and RNS can also lead to
unwanted oxidation reactions when accumulate and if they are in high amounts
they can produce toxic effects. The organism must confront and control the
presence of both pro-oxidants and antioxidants continuously. The balance
between these is tightly regulated and extremely important for maintaining
vital cellular and biochemical functions. Although the exposure of the organism
to ROS is extremely high from exogenous sources, the exposure to endogenous
sources is much more important and extensive. The dual nature of these species
with their beneficial and deleterious characteristics implies the complexities
of their specific functioning at a biological site.