Date Approved

4-2012

Graduate Degree Type

Thesis

Degree Name

Cell and Molecular Biology (M.S.)

Degree Program

Biology

Abstract

Coronary arteries supply blood to the myocardium. The blood flow within the coronary arteries is altered by various compounds produced within the body. Sex hormones such as testosterone are known to cause the relaxation of large coronary arteries. But the response to testosterone is greater in in vivo conditions compared to in vitro conditions. We hypothesize that the responses of LADs (left anterior descending arteries) and its side branches to testosterone are heterogeneous and testosterone-induced vasodilation is greater in its side branches. Therefore, our study was designed to determine the effect of testosterone in different-sized coronary arteries. LADs and one of its side branches were isolated from porcine hearts and mounted in organ baths to mimic in vivo conditions. The coronary arteries were then preconstricted with potassium chloride (KCl) and administered increasing concentrations of testosterone to determine if the responses to testosterone vary within different regions of the coronary circulation. The testosterone caused significant relaxation in both LADs and its side branches. However the side branches showed similar responses to testosterone as compared to the larger, upstream LADs. Further studies on androgen receptor expression using real time PCR indicated that androgen receptor expression was higher in LADs than its side branches. A third group of small coronary arteries exhibited greater androgen receptor expression than the LADs and its side branches. The enhanced testosterone-induced vascular reactivity exhibited in vivo may be at the level of the small coronary arteries, not the LAD and its side branches.

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