Effects of Noise Exposure on the Volume of Adrenal Gland and Serum Levels of Cortisol in Rat

Background: Noise pollution is considered as a stressful factor in every day’s life of the industrial world. The present study was designed to investigate the probable effects of different time exposure of noise stress on histomorphometric changes of adrenal gland, plasma cortisol and body weight of the rat. Methods: Sixty adult male Wistar rats were divided into two series of short time noise or STNE exposure (n=20) for one day and long time noise exposure or LTNE (n=40) for 30 days with a sound intensity of 100 dBA. LTNE series were further divided into five groups of control, sham, 4, 8 and 12-hrs noise exposure and STNE series were divided into four groups of the same as LTNE except sham group. The cortisol assay was performed on blood samples of pre and post treatment with noise in two series and Cavalieri methods in a stereological study for determination of adrenal volume changes only in LTNE series. Results: The results showed that the mean plasma cortisol level (5.4±3.2 µg/dl in LNTE-8hrs and 4.9±1.8 µg/dl in LNTE-12hrs), the volumes of cortex (7.08±1.31 mm3 in LNTE-8h and 7.12±1.31 mm3 in LNTE-12h), medulla (0.68±0.19 mm3 in LNTE-8h) of adrenal gland increased. The mean animal weight did not show any significant changes. Conclusion: Sound pollutions can increase the stress hormone level and cause increasing the volume of adrenal gland that may be related to the effect of noise on the hypothalamus-pituitary-adrenal axis. These results may be important to increasing of many disorders such as cardiovascular diseases in industrial societies.Iran J Med Sci 2006; 31(1): 5-8. Keywords ● Adrenal gland ● volume ● cortisol ● noise exposure ● stress