The transcellular pathway is a significant contributor to water flow through vascular endothelia
Item
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Title
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The transcellular pathway is a significant contributor to water flow through vascular endothelia
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Identifier
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d_2009_2013:234bc7657248:10954
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identifier
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11168
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Creator
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Xue, Yan,
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Contributor
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Karen Hubbard
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Date
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2011
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Language
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English
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Publisher
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City University of New York.
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Subject
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Physiology | Molecular biology | Biomedical engineering | AQP1 | artherosclerosis | hydraulic conducivity | organ culture | solute and water permeability | vascular endothelial cells
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Abstract
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Aquaporin-1 (AQP1) is a ubiquitous water channel protein that facilitates transmembrane water flow. The aim of our study is to determine the contribution of the AQP1 transcellular pathway to water filtration through aortic endothelial cells (AECs). In this thesis, we use both in vitro and ex vivo models of rat AECs to characterize the transport properties of such cells to water and/or small solutes.;In vitro water flux (Jv) studies show that 67.9% knockdown of AQP1 in rat AECs by small interfering RNA (siRNA) significantly reduces Jv by 56.4+/-8.2% (n=7). A study of the permeability to tetramethylrhodamine (TAMRA) and albumin has provided an interesting insight into what portion of this Jv reduction is due directly to AQP1 suppression, since these solutes traverse only inter-endothelial junctions. As a result, AQP1 suppression leads to a 21.8+/-7.04% drop in TAMRA convective permeability and a 29.79.1+/-1.72% /25.69+/-8.19% drop in albumin permeability under convection/diffusion conditions between control and treated monolayers.;We have constructed an ex vivo culture system that allows for the perfusion of the vessel lumen and application of a hydrostatic pressure that yields a physiological shear stress and transmural pressure. We note that maintenance of both pressure and shear flow preserves isolated AEC integrity, as assessed by hydraulic conductivity (Lp) and morphology studies. This culture model enables us to employ molecular manipulation of AECs in intact rat aortas. We showed that downregulation of AQP1 via siRNA results in a pressure-dependent decrease in total Lp ( Lp of endothelium + subendothelial intima (SI)), Lp t (Lpe+ i), by 37.35+/-12.97% (n=5) (59.8+/-11.6 % (n=3)) and 8.71+/-3.76% (n=5) (15.5+/-9.1% (n=3)) at 60 and 100 mmHg respectively. Our study indicates that AQP1 contributes significantly to transendothelial Lp. Transendothelial water flow is critical in determining whether low-density-lipoprotein (LDL) molecules can spend enough time at high enough local concentration in the SI to bind to SI extracellular matrix, a critical step in early atherosclerotic lesion formation. Our data suggest that regulation of AQP1, an important contributor to water filtration, may affect lipid transport in a beneficial way with regards to early disease progression.
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Type
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dissertation
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Source
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2009_2013.csv
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degree
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Ph.D.
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Program
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Biology
