No direct nuclear effect of progesterone in the inner ear: other possible pathways

Abstract

Conclusion: No nuclear progesterone receptors were found in human or rat stria vascularis, organ of Corti or spiral ganglion with immunohistochemistry or polymerase chain reaction (PCR). Progesterone receptor B (PR-B) was found with Western blot in the cochlea, probably representing the staining in the cochlear bone. The effect of progesterone on hearing is therefore most likely not due to a direct action on the inner ear. Objectives: Studies suggest that progesterone as a component in hormone replacement therapy has a negative effect on hearing thresholds and otoacoustic emissions in pre- and postmenopausal women and mice. This study was designed to examine the presence of PRs in the cochlea of humans and rats. Methods: Immunohistochemical staining of PR protein in humans and rats, PCR of PR-B mRNA expression, and Western blot of PR-A and PR-B protein in rats was performed. Results: No nuclear staining could be found for any PR in human or rat inner ear except the PR-B staining in the cochlear bone. No mRNA expression was detected by PCR. PR-B could be detected in Western blot performed on the whole cochlea including bone.

Keywords::

• Progesterone receptor
• mineralocorticoid receptor
• sex hormones
• hormone replacement therapy
• human
• rat
• cochlea
• immunohistochemistry
• PCR
• Western blot

Acknowledgments

The authors wish to thank Britt Masironi and Inna Meltser for helpful technical assistance, Paula Mannström for help with dissection of the rat cochleae, and Natalie Wisniewski for editorial support. We also wish to thank Prof. Helge Rask-Andersen and Liu Wei, ENT-Department, Uppsala University Hospital, Uppsala and Prof. Annelise Schrott-Fischer, Innsbruck, Austria for kind support and donation of human inner ear sections. This study was supported by grants from KI-fonder 2008Fobi0462 and Acta Otolaryngologica.

Declaration of interest: The authors report no conflicts of interest. The authors alone are responsible for the content and writing of the paper.