title: Low-affinity transport of pyroglutamyl-histidine in renal brush-border membrane vesicles.
abstract: These studies were performed to determine if a low-affinity carrier is present in the luminal membrane of proximal tubular cells for the transport of the dipeptide, pyroglutamyl-histidine (pGlu-His). We have previously described the existence of a specific, high-affinity, low-capacity [transport constant (Kt) = 9.3 X 10(-8) M, Vmax = 6.1 X 10(-12) mol.mg-1.min-1] carrier for pGlu-His in renal brush-border membrane vesicles. In the present study, we sought to demonstrate that multiple carriers exist for the transport of a single dipeptide by determining whether a low-affinity carrier also exists for the uptake of pGlu-His. Transport of pGlu-His into brush-border membrane vesicles was saturable over the concentration range of 10(-5)-10(-3) M, yielding a Kt of 6.3 X 10(-5) M and a Vmax of 2.2 X 10(-10) mol.mg-1.min-1. Uptake was inhibited by the dipeptides glycyl-proline, glycyl-sarcosine, and carnosine but not by the tripeptide pyroglutamyl-histidyl-prolinamide. We conclude that 1) pGlu-His is transported across the luminal membrane of the proximal tubule by multiple carriers and 2) the lower affinity carrier, unlike the higher affinity carrier, is nonspecific with respect to other dipeptides.
authors.affiliation: Department of Physiology, University of Health Sciences, Chicago Medical School, Illinois.
authors.forename: H A
authors.initials: HA
authors.lastname: Skopicki
authors.forename: K
authors.initials: K
authors.lastname: Fisher
authors.forename: D
authors.initials: D
authors.lastname: Zikos
authors.forename: G
authors.initials: G
authors.lastname: Flouret
authors.forename: D R
authors.initials: DR
authors.lastname: Peterson
mesh_terms: D001692:Biological Transport; D004151:Dipeptides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D006868:Hydrolysis; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008871:Microvilli / Q000378:metabolism; D009994:Osmolar Concentration; D010455:Peptides / Q000494:pharmacology; D011761:Pyrrolidonecarboxylic Acid / Q000031:analogs & derivatives; D013997:Time Factors
chemical_list: D004151:Dipeptides; D010455:Peptides; C058050:pyroglutamylhistidine; D011761:Pyrrolidonecarboxylic Acid