Noise Induced Changes of Glucocorticoid Receptors in Rat Cocohlea

You, Jong Seon; Lim, Hyun Ho; Choi, Jong Ouck

Abstract

It has been suggested that glucocorticoid receptors are present in inner ear tissues and may act in stress related mechanism of cochlea. The purpose of this study was to determine whether stress to auditory system could change glucocorticoid receptors(GR) in the cochlear tissues and to hypothesize the relationship between heat shock protein and glucococorticoid receptors which may involve in stress related mechanism of cochlea. Sprague-Dawley rats were exposed to intense broad band noise(110dB SPL) as a stressful condition to auditory system and immunohistochemical and western blot analyses were used to compare the expression patterns of glucocorticoid receptors between noise exposed and normal rat cochlea. In western blot analysis, immunoreactive bands of noise exposed cochlear tissues were weaker than those of normal non-noise exposed cochlear tissues. In immunohistochemistry, GR immunostaining was observed in spiral ligament, stria vascularis, and outer hair cells of both noise exposed and normal cochlear tissues. Density of immunoreactive staining was decreased after noise exposure. With these results was could hypothesize the relationship between glucocorticoid receptor and heat shock proteins under stressful condition in the cochlea. If the cochlea is exposed to stress such as noise trauma, glucocorticoid hormone would be released and enter the cell to bind to glucocorticoid receptors with dissociation of heat shock proteins from the DNA binding sites. Then the levels of glucocorticoid receptors in the cytoplasm would be decreased and resultant increased expression of heat shock proteins may occur. This study suggest that glucocorticoid receptors may participate in stress response of the cochlea alone or in conjunction with heat shock proteins.