title: Peptide uptake by astroglia-rich brain cultures.
abstract: Uptake of carnosine has been investigated in astroglia-rich primary cultures derived from brains of newborn mice. It could be demonstrated that carnosine is not degraded by these cells but rapidly taken up in an energy- and sodium-dependent process. Uptake and release of carnosine by these cells were found to be mediated by a saturable, high-affinity transport system with apparent kinetic constants of Km = 50 microM and Vmax = 22.7 nmol X h-1 X mg protein-1. Uptake of carnosine is strongly inhibited by other dipeptides as well as by various oligopeptides, e.g., Leu-enkephalin. However, uptake of the radiolabeled tripeptide D-Ala-L-Ala-L-Ala was not observed. Radiolabeled Leu-enkephalin also did not accumulate intracellularly, even if degradation of the peptide was prevented by use of peptidase inhibitors. These results suggest that uptake of carnosine is catalyzed by a dipeptide-specific transport system with broad substrate specificity. With neuronal cells in primary culture, uptake of carnosine or other peptides was not observed.
mesh_terms: D000596:Amino Acids / Q000494:pharmacology; D000818:Animals; D001921:Brain / Q000166:cytology* / Q000196:embryology / Q000378:metabolism; D002336:Carnosine / Q000378:metabolism; D002478:Cells, Cultured; D004151:Dipeptides / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004734:Energy Metabolism; D005260:Female; D007700:Kinetics; D009457:Neuroglia / Q000378:metabolism*; D010455:Peptides / Q000378:metabolism*; D011247:Pregnancy; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism
chemical_list: D000596:Amino Acids; D004151:Dipeptides; D010455:Peptides; D002336:Carnosine; D012964:Sodium