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Lookup NU author(s): Professor David Thwaites,
Professor Nicholas Simmons
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The nature of transepithelial and cellular transport of the dibasic amino acid lysine in human intestinal epithelial Caco-2 cells has been characterized. Intracellular accumulation of lysine across both the apical and basolateral membranes consists of a Na+-independent, membrane potential-sensitive uptake. Na+-independent lysine uptake at the basolateral membrane exceeds that at the apical membrane. Lysine uptake consists of both saturable and nonsaturable components. Na+-independent lysine uptake at both membranes is inhibited by lysine, arginine, alanine, histidine, methionine, leucine, cystine, cysteine and homoserine. In contrast, proline and taurine are without inhibitory effects at both membranes. Fractional Na+-independent lysine efflux from preloaded epithelial layers is greater at the basolateral membrane and shows trans-stimulation across both epithelial borders by lysine, arginine, alanine, histidine, methionine, and leucine but not proline and taurine. Na+-independent lysine influx (10 μM) in the presence of 10 mM homoserine shows further concentration dependent inhibition by lysine. Taken together, these data are consistent with lysine transport being mediated by systems b0,+, y+ and a component of very low affinity (nonsaturable) at both membranes. The relative contribution to lysine uptake at each membrane surface (at 10 μM lysine), normalized to total apical uptake (100%), is apical b0,+ (47%), y+ (27%) and the nonsaturable component (26%), and basal b0,+ (446%), y+ (276%) and the nonsaturable component (20%). Northern analysis shows hybridization of Caco-2 poly(A)+RNA with a human rBAT cDNA probe.
Author(s): Simmons NL; Thwaites DT; Markovich D; Murer H
Publication type: Article
Publication status: Published
Journal: Journal of Membrane Biology
Print publication date: 01/01/1996
ISSN (print): 0022-2631
ISSN (electronic): 1432-1424
Publisher: Springer New York LLC
PubMed id: 8661509
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