H(+)-glycyl-L-proline cotransport in brush-border membrane vesicles of eel (Anguilla anguilla) intestine

Abstract

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.

Characterisation of intestinal peptide transporter of the Antarctic haemoglobinless teleostChionodraco hamatus

“…2A), with a relatively low substrate specificity, as it has generally been found for the PepT1 isoforms studied to date ( Fig. 2B; Ganapathy et al, 1994;Liang et al, 1995;Thamotharan et al, 1996;Maffia et al, 1997;Verri et al, 2000;Meredith and Boyd, 2000). Proton influx shows a hyperbolic function with substrate concentration typical of a carrier-mediated process (Fig.…”

“…Moreover, H + /glycyl-glycine, H + /glycyl-L-proline and H + /D-phenyl-L-alanine cotransport has been described in eel Anguilla anguilla intestinal BBM (Verri et al, 1992(Verri et al, , 2000Maffia et al, 1997).…”

“…Two H + /peptide cotransporters, a lower affinity PepT1 and a higher affinity PepT2, have been cloned and functionally characterised in higher vertebrates (Fei et al, 1994;Liu et al, 1995). Although the molecular structures of peptide transporters are almost unknown in teleost fish, the presence of a 'low affinity type' peptide transporter has been described in the intestinal brush border membranes of herbivorous (Oreochromis mossambicus; Thamotharan et al, 1996) and carnivorous teleosts (Sebastes caurinus and Anguilla anguilla; Verri et al, 1992;Thamotharan et al, 1996;Maffia et al, 1997). As in higher vertebrates, the peptide transporter in teleosts operates electrogenically by coupling proton translocation to substrate transport.…”

Pharmacokinetics of cephalexin in sea bream, Sparus aurata (L.), after a single intraperitoneal injection

“…Absence of adverse effects even at high doses indicates a high pharmacological manageability of the drug. Moreover, known existence of di‐ and tripeptide transport proteins (located at the apical and basolateral membranes of the enterocytes) that also mediate the lumen to blood transport of β ‐lactam antibiotics across the intestinal epithelium of teleost fish (Verri et al., 1992, 2000; Thamotharan et al., 1996a,b; Maffia et al., 1997) suggests the possibility of oral administration of this class of drugs by medicated feed, as routinely applied in fish farming. Care must be taken concerning the treatment scheme, owing to rapid elimination of the drug from serum that would require two times daily administration of the antibiotic for efficient antimicrobial treatments.…”

An l-proline-dependent proton flux is located at the apical membrane level of the eel enterocytes

“…In the intestine of the herbivorous tilapia (Oreochromis mossambicus) as well as in the intestine and pyloric ceca of the carnivorous rockfish (Sebastes caurinus), the uptake of a dipeptide (glycil-sarcosine) at the apical membrane level was found to be stimulated by an inwardly directed transmembrane proton gradient (12). Similarly, in the intestine of the euryhaline teleost Anguilla anguilla, proton-dependent dipeptide transporters have been characterized (5,17). However, a facilitated transport system for glycil-L-phenylalanine has been characterized in brush-border membrane vesicles (BBMV) isolated from tilapia intestinal absorbing cells (6).…”