An electrogenic amino acid transporter in the apical membrane of cultured human bronchial epithelial cells.
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.
Galietta
L J
LJ
Laboratorio di Genetica Molecolare, Istituto Giannina Gaslini, 16148 Genoa, Italy.
Musante
L
L
Romio
L
L
Caruso
U
U
Fantasia
A
A
Gazzolo
A
A
Romano
L
L
Sacco
O
O
Rossi
G A
GA
Varesio
L
L
Zegarra-Moran
O
O
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
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