H(+)-glycyl-L-proline cotransport in brush-border membrane vesicles of eel (Anguilla anguilla) intestine.
A plasma membrane H(+)-glycyl-L-proline (Gly-L-Pro) cotransport mechanism has been identified in isolated eel intestinal brush-border membrane vesicles (BBMV) by both measuring radiolabeled Gly-L-Pro uptake and monitoring Gly-L-Pro-dependent H+ influx with the pH-sensitive dye acridine orange. The application of an inside negative membrane potential resulted in increasing Gly-L-Pro uptake, as well as the application of inwardly directed H+ gradient (although only when an inside negative membrane potential was present). Furthermore, vesicular H+ influx was found specifically associated with the presence of Gly-L-Pro in the extravesicular medium. The carrier-mediated nature of H(+)-Gly-L-Pro cotransport was assessed, and its concentration that yielded one-half maximal Gly-L-Pro influx was approximately 1.30 mM when measured by either radioactive or fluorescent tracers. Different dipeptides strongly inhibited Gly-L-Pro uptake by eel intestinal BBMV, as well as the cephalosporin antibiotic cephalexin, suggesting that dipeptide molecules and cephalosporin antibiotics may share a common transport system in eel intestinal BBMV.
Maffia
M
M
Dipartimento di Biologia, Università di Lecce, Italy. physiol@mgle01.unile.it
Verri
T
T
Danieli
A
A
Thamotharan
M
M
Pastore
M
M
Ahearn
G A
GA
Storelli
C
C
D000811:Anguilla / Q000378:metabolism*; D000818:Animals; D001692:Biological Transport; D004151:Dipeptides / Q000493:pharmacokinetics*; D005453:Fluorescence; D006859:Hydrogen / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D007413:Intestinal Mucosa / Q000378:metabolism*; D007422:Intestines / Q000502:physiology; D007700:Kinetics; D008564:Membrane Potentials; D008871:Microvilli / Q000378:metabolism / Q000502:physiology; D013379:Substrate Specificity
D004151:Dipeptides; C015248:glycylproline; D006859:Hydrogen