Effect of noise stress on free radical scavenging enzymes in brain.

The levels of free radical scavenging enzymes in six discrete brain regions (cerebral cortex, cerebellum, midbrain, pons medulla, hippocampus and hypothalamus), after exposure to three different durations of noise stress (broadband white noise, 100dB, 4h/day, in acute: 1 day, sub acute: 15 days and chronic stress: 30 days) was studied in Wister strain male albino rats. Acute noise stress significantly increases the levels of superoxide dismutase (SOD: EC 1.15.1.1), catalase (EC 1.11.1.6), glutathione peroxidase (GPx: EC 1.11.1.9), oxidized glutathione (GSSG) and lipid peroxidation (LPO) and decreases the levels of reduced glutathione (GSH), GSH/GSSG ratio and protein thiols. The free radical scavenging enzymes levels, in sub acute and chronic noise stress also showed marked deviation in certain regions from the controls within the study duration. The results indicate that adaptation to noise stress does not occur immediately in all the brain regions. The noise induced alterations in free radicals may be assumed to serve as a linkage between the environmental noise and the manifestation of multifactorial diseases attributed to noise exposure. Moreover the quantification of the health effects of noise by the alterations in free radicals seems inappropriate in chronic noise stress.