Cloning and characterization of a rat H+/peptide cotransporter mediating absorption of beta-lactam antibiotics in the intestine and kidney.
A complementary DNA (cDNA) encoding the rat H+/peptide cotransporter (PepT1) was isolated, and the transport characteristics of orally active beta-lactam antibiotics were assessed by measuring uptake into Xenopus oocytes expressing the rat PepT1. The rat PepT1 cDNA encoded a 710-amino acid protein with 77% identity to the rabbit PepT1. The message for rat PepT1 was approximately 2.9 kilobases and was found predominantly in the small intestine, whereas reverse transcription-polymerase chain reaction amplification revealed that the message was expressed both in the small intestine and in the kidney cortex. The 75-kDa protein was identified by translation of in vitro synthesized transcript of rat PepT1 cDNA by use of rabbit reticulocyte lysates and by Western blot analysis with a specific antibody against the rat PepT1. When expressed in Xenopus oocytes, rat PepT1 stimulated the uptake of ceftibuten (anion) and cephradine (zwitterion) in the presence of an inward H+ gradient, and the expressed uptake was inhibited by excess dipeptides. Kinetic analysis revealed that ceftibuten has 14-fold higher affinity for the rat PepT1 than cephradine. These findings suggest that the rat PepT1 mediates H(+)-coupled uphill transport of the oral beta-lactam antibiotics across the brush-border membranes of intestinal and renal proximal tubular cells.
Saito
H
H
Department of Pharmacy, Kyoto University Hospital, Faculty of Medicine, Japan.
Okuda
M
M
Terada
T
T
Sasaki
S
S
Inui
K
K
D000595:Amino Acid Sequence; D000818:Animals; D000900:Anti-Bacterial Agents / Q000493:pharmacokinetics*; D001483:Base Sequence; D001692:Biological Transport; D015153:Blotting, Western; D015820:Cadherins; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003001:Cloning, Molecular; D018076:DNA, Complementary; D007408:Intestinal Absorption; D007668:Kidney / Q000378:metabolism*; D008297:Male; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D010455:Peptides / Q000378:metabolism; D011522:Protons; D011817:Rabbits; D051381:Rats; D017207:Rats, Sprague-Dawley; D017386:Sequence Homology, Amino Acid; D014981:Xenopus; D047090:beta-Lactams
D000900:Anti-Bacterial Agents; D015820:Cadherins; D002352:Carrier Proteins; C490586:Cdh17 protein, rat; D018076:DNA, Complementary; D026901:Membrane Transport Proteins; D010455:Peptides; D011522:Protons; D047090:beta-Lactams; C067802:intestinal peptide-proton cotransporter