Abstract

Thyroid hormone (TH) is essential for the development and maturation of the nervous system. The thyroid gland secretes an active form of TH, triiodothyronine, and a prohormone, thyroxine, into the blood. TH is charged, which prevents it from passively diffusing across cell membranes and thus requires cell membrane transporters to facilitate its movement into and out of cells. However, whether TH transporters are required for TH-mediated developmental events, including the auditory system, is largely unknown.

The purpose of the present study was to investigate two specific TH transporters, monocarboxylate transporter 8 (Mct8) and organic anion transporting polypeptide 1c1 (Oatp1c1), and their role in the development and function of the auditory system. Development was observed by comparing key structures within the cochlea necessary for normal hearing between mice lacking each transporter individually or in combination by taking measurements from histological sections. Histological analysis demonstrated no significant difference in the size of the tectorial membrane, tunnel of Corti, or greater epithelial ridge between any of the genotypes. To test the auditory function and the integrity of the auditory pathway, auditory-evoked brainstem response (ABR) was evaluated. ABR data demonstrated that mice lacking both Mct8 and Oatp1c1 (double KO mice), as compared to wildtype, had significantly elevated hearing thresholds at 32kHz, but not at 8kHz or 16kHz. Furthermore, analysis of ABR waveforms demonstrated significantly slower latencies at all frequencies tested. Taken together, these results suggest cochlear structure is largely normal in the absence of TH transporters MCT8 and Oatp1c1, but that these transporters play an essential role in the processing of auditory signals through the brain stem.

Advisor

David Sharlin

First Committee Member

Michael Bentley

Second Committee Member

Geoffrey Goellner

Date of Degree

2014

Language

english

Document Type

Thesis

Degree

Master of Science (MS)

Department

Biological Sciences

College

Science, Engineering and Technology

Creative Commons License

Creative Commons Attribution-Noncommercial 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License

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