Oral absorption of ampicillin: role of paracellular route vs. PepT1 transporter.
The beta-lactam antibiotic ampicillin has a relatively poor oral bioavailability in animals and man (30-40%), and its widespread agricultural use in livestock may be contributing to the emergence of antibiotic resistance in the environment. The aim of this study was to define the absorption mechanism by which ampicillin crosses the small intestinal epithelium. The improved rat everted gut sac system was used, with an emphasis on the role of the PepT1 transporter. The absorption kinetics, effects of pH and the use of competitive substrates failed to provide any substantive evidence that the transporter played a major role in ampicillin absorption. Ethylenediaminetetraacetic acid enhanced the absorption, and tissue levels remained low, suggesting that paracellular transport was predominant. pH and competition studies with glycylsarcosine, the widely used PepT1 substrate, also failed to show any transporter activity. Despite evidence from studies with Caco-2 cells that beta-lactam antibiotics are transported by the PepT1 transporter in rat small intestine, the results rather suggest that paracellular diffusion is the major mechanism of absorption, at least for beta-lactam antibiotics with poor bioavailability, such as ampicillin. We suggest that the use of Caco-2 cells underestimates the role of the paracellular route in the absorption of hydrophilic drugs in vivo, and may exaggerate the role of influx transporters.
Lafforgue
Guylène
G
Laboratoire Cinétique des Xénobiotiques, Faculté des Sciences Pharmaceutiques, 35 Chemin des Maraîchers, 31062 Toulouse cedex 4, France.
Arellano
Cécile
C
Vachoux
Christelle
C
Woodley
John
J
Philibert
Claude
C
Dupouy
Veronique
V
Bousquet-Mélou
Alain
A
Gandia
Peggy
P
Houin
Georges
G
D000667:Ampicillin / Q000378:metabolism* / Q000493:pharmacokinetics; D000818:Animals; D000900:Anti-Bacterial Agents / Q000378:metabolism* / Q000493:pharmacokinetics; D001682:Biological Availability; D001692:Biological Transport; D002614:Chelating Agents / Q000494:pharmacology; D004151:Dipeptides / Q000493:pharmacokinetics; D004492:Edetic Acid / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007408:Intestinal Absorption; D007421:Intestine, Small / Q000378:metabolism*; D008297:Male; D009077:Mucins / Q000502:physiology; D000074011:Peptide Transporter 1; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D027981:Symporters / Q000096:biosynthesis* / Q000235:genetics
D000900:Anti-Bacterial Agents; D002614:Chelating Agents; D004151:Dipeptides; D009077:Mucins; D000074011:Peptide Transporter 1; D012333:RNA, Messenger; D027981:Symporters; C004194:glycylsarcosine; D000667:Ampicillin; D004492:Edetic Acid