Despite advancement in the understanding of microhomeostatic mechanisms involved in ionic and fluid gradients within the inner ear, the means by which such cellular activities are regulated remain unresolved. Recent findings in the applicant's laboratory have demonstrated presence of receptors for adrenal steroids within tissues of both the cochlear duct and vestibular endorgans. Adrenal steroids have been shown to be involved in ion and fluid regulation elsewhere in the body. When circulating adrenal steroids were removed via bilateral adrenalectomy, biochemical and morphological changes of select inner ear nonsensory epithelia were observed. Such findings indicate that adrenal steroids modify inner ear tissues via a neuroendocrine system. These data are the first to implicate the role of adrenal steroids in inner ear microhomeostasis. The objective of this investigation is to localize and characterize adrenal steroid receptors within inner ear tissues using immunocytochemistry, quantitative morphometry and transmission electron microscopy. Adrenal steroid receptors in inner ear tissues from experimental animals will be detected by the monoclonal antibody (BuGRI) to the adrenal steroid receptors II/IB and protein A colloidal gold complexes. Positive control tissues will be processed in parallel to those of the inner ear. Under prescribed experimental conditions, adrenalectomized animals will be administered differing concentrations of aldosterone or dexamethasone with and without their antagonists. These data will provide further insight into the dynamics of the adrenal steroid system as it relates to location, density and binding characteristics of the adrenal steroid receptors within the inner ear. Such findings will provide insight into how steroid therapy, including dexamethasone, influences the structural and functional integrity of the inner ear.
