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Glucocorticoid receptors in the mammalian inner ear: RU 28362 binding sites
D Z Pitovski1, M J Drescher, D G Drescher
1Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, MI 48201.
Hearing Research
|June 15, 1994
Summary
This study identified glucocorticoid receptors in the inner ear using [3H]-RU 28362. These receptors are present in the cochlea and semicircular canals, suggesting sites for glucocorticoid hormone action.
Area of Science:
- Otolaryngology
- Endocrinology
- Molecular Biology
Background:
- Glucocorticoid hormones exert effects via intracellular receptors.
- Identifying these receptors in the inner ear is crucial for understanding local hormone action.
Purpose of the Study:
- To identify and characterize high-affinity glucocorticoid (Type II) receptors in the inner ear.
- To determine the concentration and distribution of these receptors in cochlear and vestibular tissues.
Main Methods:
- Utilized the synthetic glucocorticoid [3H]-RU 28362, selective for Type II receptors.
- Employed Scatchard analysis to quantify receptor binding affinity (Kd) and concentration (Bmax).
- Investigated binding kinetics through time course studies at 25°C.
Main Results:
- [3H]-RU 28362 demonstrated high-affinity binding to inner ear tissues.
- Kd values for the cochlear lateral wall and ampullae were approximately 11.4 nM and 12.7 nM, respectively.
- Glucocorticoid receptor concentration was higher in the cochlear lateral wall (240 fmol/mg) compared to the ampullae (89 fmol/mg).
Conclusions:
- Specific binding of [3H]-RU 28362 confirms the presence of glucocorticoid receptors in the inner ear.
- The findings indicate potential sites of glucocorticoid hormone action within the cochlea and vestibular system.
- Glucocorticoid receptor density is significantly higher in the cochlear lateral wall than in the ampullae.