title: An electrogenic amino acid transporter in the apical membrane of cultured human bronchial epithelial cells.
abstract: We performed Ussing chamber experiments on cultured human bronchial epithelial cells to look for the presence of electrogenic dibasic amino acid transport. Apical but not basolateral L-arginine (10-1, 000 microM) increased the short-circuit current. Maximal effect and EC50 were approximately 3.5 microA/cm2 and 80 microM, respectively, in cells from normal subjects and cystic fibrosis patients. The involvement of nitric oxide was ruled out because a nitric oxide synthase inhibitor (NG-nitro-L-arginine methyl ester) did not decrease the arginine-dependent current. Apical L-lysine, L-alanine, and L-proline, but not aspartic acid, were also effective in increasing the short-circuit current, with EC50 values ranging from 26 to 971 microM. Experiments performed with radiolabeled arginine demonstrated the presence of an Na+-dependent concentrative transporter on the apical membrane of bronchial cells. This transporter could be important in vivo to maintain a low amino acid concentration in the fluid covering the airway surface.
authors.affiliation: Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, 16148 Genoa, Italy.
authors.forename: L J
authors.initials: LJ
authors.lastname: Galietta
authors.forename: L
authors.initials: L
authors.lastname: Musante
authors.forename: L
authors.initials: L
authors.lastname: Romio
authors.forename: U
authors.initials: U
authors.lastname: Caruso
authors.forename: A
authors.initials: A
authors.lastname: Fantasia
authors.forename: A
authors.initials: A
authors.lastname: Gazzolo
authors.forename: L
authors.initials: L
authors.lastname: Romano
authors.forename: O
authors.initials: O
authors.lastname: Sacco
authors.forename: G A
authors.initials: GA
authors.lastname: Rossi
authors.forename: L
authors.initials: L
authors.lastname: Varesio
authors.forename: O
authors.initials: O
authors.lastname: Zegarra-Moran
mesh_terms: D000409:Alanine / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D026905:Amino Acid Transport Systems; D000596:Amino Acids / Q000494:pharmacology*; D001120:Arginine / Q000494:pharmacology; D001980:Bronchi / Q000502:physiology*; D002352:Carrier Proteins / Q000378:metabolism*; D002462:Cell Membrane / Q000187:drug effects / Q000502:physiology*; D002478:Cells, Cultured; D004847:Epithelial Cells / Q000187:drug effects / Q000502:physiology*; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000494:pharmacology; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D020030:Nitric Oxide Donors / Q000494:pharmacology; D010396:Penicillamine / Q000031:analogs & derivatives / Q000494:pharmacology; D011392:Proline / Q000494:pharmacology; D026423:S-Nitroso-N-Acetylpenicillamine
chemical_list: D026905:Amino Acid Transport Systems; D000596:Amino Acids; D002352:Carrier Proteins; D020030:Nitric Oxide Donors; D026423:S-Nitroso-N-Acetylpenicillamine; D000584:Amiloride; D001120:Arginine; D011392:Proline; D010396:Penicillamine; D008239:Lysine; D000409:Alanine