The characteristics of carnosine transport and carnosine-induced electrical phenomena by the everted intestine of guinea pig.
The properties of carnosine (Car) and glycylglycine (Gly-Gly), transported across the mucosal border, were studied in isolated guinea pig everted ileum. The initial influxes of both dipeptides could be described by single Michaelis-Menten kinetics, having a nearly equal value of maximum influx. Mutual inhibition studies showed that the inhibition observed between Car and Gly-Gly was fully competitive, indicating that both Car and Gly-Gly share a common carrier. Although carrier-mediated influxes of the dipeptides were independent of Na+, the addition of the dipeptides into the mucosal solution evoked sudden and sustained increments of mucosal negativity. The changes in short-circuit current (delta Isc) evoked by the peptides increased as the Na+ concentration in the solution was increased, although both dipeptides evoked small increases in Isc, even in the absence of Na+. In spite of these common properties of transport and transport-related electrical phenomena, it was seen that the maximum change in transmural potential difference (delta PDt max) evoked by Car was about half that of Gly-Gly. Such a discrepancy between coincident Jmax values and values of delta PDt max suggests that the mechanism of induction of ionic flow is different for these two dipeptides.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002336:Carnosine / Q000378:metabolism* / Q000494:pharmacology; D004151:Dipeptides / Q000378:metabolism*; D004553:Electric Conductivity; D006033:Glycylglycine / Q000378:metabolism; D006168:Guinea Pigs; D007082:Ileum / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D007413:Intestinal Mucosa / Q000187:drug effects / Q000502:physiology*; D007700:Kinetics; D008564:Membrane Potentials / Q000187:drug effects; D015091:beta-Alanine / Q000378:metabolism
D004151:Dipeptides; D006033:Glycylglycine; D015091:beta-Alanine; D002336:Carnosine