The Liver as a Target Organ for the Non-Genomic Actions of Estrogen
"Estrogen, as well as all other steroid hormones tested, display rapid (seconds to minutes) effects which are not consistent with the classical, genomic responses in target cells. These effects, because of their rapidity and apparent independence from the genome, are termed ""non-genomic"". It is the goal of this thesis to identify tissues which display a non-genomic response to a radioiodinated, estrogencontaining ligand, which cannot enter cells by diffusion due to a large protein component, in vivo in rats. Furthermore, I will discuss the cellular response generated by this non-genomic interaction, identify the intracellular targets for the ligand, and isolate and identify a membrane protein which binds the ligand and free estradiol. I present results which identify the liver as a major tissue with a non-genomic response to estrogen, namely, the uptake and translocation of the ligand from a plasmalemmal and microsomal membrane fraction (P3) to a mitochondrial and lysosomal membrane fraction (P2). I also investigate the binding characteristics of the P3 fraction and potential binding proteins from the P3 fraction. I then use a colloidal gold-labeled, estrogen-containing ligand and electron microscopy of Hep G2 cells to directly visualize the uptake and translocation of the ligand. I confirm the receptor-mediated endocytosis of the ligand and identify the mitochondria as an intracellular target for the ligand. Using affinity chromatography, I isolate a protein which is identified as cholesterol ester hydrolase, a major enzyme in the intracellular cholesterol ester cycle. Moreover, I show that this enzyme may respond to estrogen by increasing its rate of hydrolysis. Finally, I summarize my results and discuss the implications of the data for human health."
University of Illinois - Urbana-Champaign
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University of Illinois at Urbana-Champaign