Year of Publication

2018

Degree Name

Master of Science (MS)

Document Type

Master's Thesis

College

Agriculture, Food and Environment

Department

Veterinary Science

First Advisor

Dr. Alejandro Esteller-Vico

Abstract

The objectives of this study are to characterize two carrier proteins in the horse that significantly decrease in humans following anabolic androgenic steroid administration: sex hormone-binding globulin (SHBG) and thyroxine-binding globulin (TBG). For SHBG characterization, qPCR, RNA sequencing, and immunohistochemistry were performed on testes and equine livers. Free and total testosterone immunoassays were utilized to confirm the presence of a carrier protein in equine circulation. SHBG was detected in the testes using qPCR, RNA sequencing, and IHC, indicating the presence of the isoform androgen-binding protein (ABP). SHBG was not detected in any liver samples. Evidence of a carrier protein was shown by free testosterone being significantly lower than the total testosterone that was detected in stallions (p < 0.0001) and pregnant mares (p < 0.0001). TBG characterization was completed using an equine specific TBG ELISA. Equine serum was analyzed across seasons, reproductive statuses, sexes, and ages. TBG concentrations were also measured following anabolic steroid administration (Stanozolol) and increased endogenous androgen production via hCG administration in stallions and aromatase inhibition via Letrozole administration in pregnant mares. TBG did not significantly differ across season, reproductive status, sex, or age Alterations of androgen concentrations did not result in any significant changes to circulating TBG concentrations.

Digital Object Identifier (DOI)

https://doi.org/10.13023/etd.2018.353

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