Umapati Sahaya, R.P. Singhb, Anita Jhac, Manjula Kumarid Hem Srivastave & A.P.V. Khalkhof
a*Dept of Zoology, R.U., Ranchi, Jharkhand, India
bDept. of Zoology, Marwari College, Ranchi, Jharkhand, India
cDept. of Zoology, Gardani Bagh, Govt. Girls’ College, Patna, Bihar, India
dDept. of Botany, Gardani Bagh, Women’s College, Patna, Bihar, India
eEx-Research Scholar, Zoology Dept., R.U., Jharkhand, India
fWomen’s College, Chaibasa, K.U., Jharkhand, India
Received , 15th December, 2012 ;Revised: 15th January, 2013
Abstract :High concentration of O2 in the body becomes toxic and leads to tissue damage. Oxygen toxicity involves oxygen free radicals or reactive oxygen species commonly called ROS. ROS are byproducts of normal metabolism. Oxygen is essential for metabolism, in which molecular oxygen is completely reduced, the final product being H2O; yet if reduction is incomplete, a number of reactive radicals are formed such as O.- 2(super oxide), H2O2 (hydrogen peroxide), O.-H(hydroxyl radical). In addition, 1O2 (singlet oxygen), HOO- (hydroperoxy radical), ROO- (lipid peroxide), NO- (nitrogen monoxide radical) and ONOO- (peroxinitrite) too are important from biological point of view. These free radicals are short lived, highly reactive and have a capacity to damage biomolecules, cells and tissues and are also capable of generating new radicals by chain reactions. There are two categories of radicals -1. A free radical contains one or more unpaired electrons (Exp. O.- 2, O.H-, R.OO–) but 2. Non free radical derivatives (without unpaired electrons) are H2O2, 1 O2.
The latter category also comes from biological systems. These radicals cause cellular damage reading to cellular injury (damages to carbohydrate, lipids, protein, RNA and DNA) and cause cell death. Excessive generation of ROS results into oxidative stress leading to pathological disorders such as cardiovascular, neurological, pulmonary, dermatological, diabetic condition, skeletal and neoplastic diseases. Redox active toxicants cause oxidative stress. The authors have described and compiled informations of these radicals, their good and bad aspects with special reference to environmental pollutants (asbestos, crystalline silica, coal, cigarette smoke, agricultural dust, inorganic dust and metal ions). They have also dealt with Lung epithelial lining versus ROS, Ischemia versus ROS, NF-kB versus ROS, inactivation of P53 (transcriptional activator) in the light of works done by various authors. The ROS, their formation and consequences have been explained with the help of suitable diagrams.