Glucocorticoid receptors in the mammalian inner ear: RU 28362 binding sites.
The effects of glucocorticoid hormones are thought to be initiated by binding of the steroid to stereospecific intracellular receptor proteins in target tissues. The synthetic glucocorticoid [3H]-RU 28362, which demonstrates negligible affinity for mineralocorticoid (Type I) receptors [Philibert et al., (1983) Endocrine Soc. Abstr. 65, 335], was employed to identify the high-affinity glucocorticoid (Type II) receptors in the inner ear. By Scatchard analysis, the Kd of the [3H]-RU 28362-cytoplasmic receptor complex was 11.4 x 10(-9) M for the lateral wall of the basal turn of the cochlea and 12.7 x 10(-9) M for the ampullae of the semicircular canals. The concentration of binding sites, Bmax, was 240 fmol/mg dry tissue for the cochlear specimen and 89 fmol/mg dry tissue for the ampullae. Time course studies indicated that the binding of [3H]-RU 28362 by inner ear tissues reached equilibrium within 30 min of incubation at 25 degrees C. Based on the total specific binding measured with [3H]-RU 28362, the glucocorticoid receptor concentration in the lateral wall of the basal turn of the cochlea appears to exceed that in the ampullae of the semicircular canal by a factor of 2.7. Substantial specific [3H]-RU 28362 binding to the cochlear lateral wall and ampullar tissue suggests the presence of glucocorticoid receptors and sites of glucocorticoid action in the inner ear.
Pitovski
D Z
DZ
Department of Otolaryngology-Head and Neck Surgery, Wayne State University School of Medicine, Detroit, MI 48201.
Drescher
M J
MJ
Drescher
D G
DG
D000732:Androstanols / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D003051:Cochlea / Q000378:metabolism*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D007700:Kinetics; D008297:Male; D011965:Receptors, Glucocorticoid / Q000145:classification / Q000378:metabolism*; D012665:Semicircular Canals / Q000378:metabolism*
D000732:Androstanols; D011965:Receptors, Glucocorticoid; C049154:11,17-dihydroxy-6-methyl-17-(1-propynyl)androsta-1,4,6-triene-3-one