title: Transport of neutral, cationic and anionic amino acids by systems B, b(o,+), X(AG), and ASC in swine small intestine.
abstract: Amino acid influx across the brush border membrane of the intact pig ileal epithelium was studied. It was examine whether in addition to system B, systems ASC and b(o,+) were involved in transport of bipolar amino acids. The kinetics of interactions between lysine and leucine demonstrates that system b(o,+) is present and accessible also to L-glutamine. D-aspartate (K(1/2) 0.3 mM) and L-glutamate (K(i) 0.5 mM) share a high affinity transporter with a maximum rate of 1.3 micromol cm(-2) h(-1), while only L-glutamate with a K(1/2) of 14.4 mM uses a low affinity transporter with a maximum rate of 2. 7 micromol cm(-2) h(-1), system ASC, against which serine has a K(i) of 1.6 mM. In the presence of 100 mM lysine, L-glutamine (A), leucine (B), and methionine (C) fulfilled the criteria of the ABC test for transport by one and the same transporter. However, serine inhibits not only transport of L-glutamate but also of glutamine (K(i) 0.5 mM), and L-glutamate inhibits part of the transport of glutamine. The test does, therefore, only indicate that the three bipolar amino acids have similar affinities for transport by systems B and ASC. Further study of the function of system B must be carried out under full inhibition by lysine and glutamate.
authors.affiliation: Department of Internal Medicine, Koge Hospital, DK-4600, Koge, Denmark. nulk@dadlnet.dk
authors.forename: L K
authors.initials: LK
authors.lastname: Munck
authors.forename: M L
authors.initials: ML
authors.lastname: Grondahl
authors.forename: J E
authors.initials: JE
authors.lastname: Thorboll
authors.forename: E
authors.initials: E
authors.lastname: Skadhauge
authors.forename: B G
authors.initials: BG
authors.lastname: Munck
mesh_terms: D000596:Amino Acids / Q000378:metabolism*; D000818:Animals; D000838:Anions; D001692:Biological Transport; D002412:Cations; D005260:Female; D007421:Intestine, Small / Q000378:metabolism*; D007700:Kinetics; D008871:Microvilli / Q000378:metabolism; D013552:Swine
chemical_list: D000596:Amino Acids; D000838:Anions; D002412:Cations