Transport ofl-lysine by rat intestinal brush border membrane vesicles |
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Authors: | G. Cassano B. Leszczynska H. Murer |
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Affiliation: | (1) Department of Physiology, University of Zürich, Rämistrasse 69, CH-8028 Zürich, Switzerland |
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Abstract: | Brush border membranes were isolated from rat jejunum by a divalent cation precipitation method.3H-l-Lysine uptake was measured by a rapid filtration technique. Uptake after prolongued incubation periods was osmotically insensitive and represented almost exclusively binding to the vesicles. Extrapolating initial linear uptake to a zero incubation time indicated no binding of the amino acid to the external membrane surface.Sodium did not significantly alter the initial uptake rate.l-Lysine transport respresents a carrier mediated uptake in the presence and absence of sodium as indicated by the transstimulation experiments. The transport mechanism operates stereospecifically and is inhibited by other basic amino acids andl-leucine andl-phenylalanine. Saturation experiments result in aKm of 0.26 mmoles/l and aVmax of 272 pmoles/mg protein/10 s.Inside negative anion diffusion potentials and inside negative potassium diffusion potentials (valinomycin) were unable to increase the transport rate. Transmembrane pH-gradients were also unable to alter transport.Abbreviations HEPES N-2-hydroxethylpiperazine-N -ethane sulfonic acid - Tris tris(hydroxymethyl)aminomethane - EGTA ethyleneglycolbis-( -aminoethyl-ether)-N,N tetraacetic acid - MES 2-(N-morpholino)-ethanesulfonic acid |
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Keywords: | font-variant:small-caps" >l-Lysine transport Small intestine Jejunum Brush border membrane Vesicles Basic amino acids |
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