title: Carrier-mediated reabsorption of small peptides in renal proximal tubule.
abstract: Recent studies with a variety of tissue preparations in the kidney have demonstrated that proximal tubular cells possess specific transport systems for di- and tripeptides. In contrast to the well-known amino acid and glucose transport systems, active transport of peptides in these cells is energized by an H+ gradient rather than an Na+ gradient. Like amino acid-Na+ and glucose-Na+ cotransport systems, peptide-H+ cotransport is electrogenic and hence a membrane potential also contributes to the uphill transport of peptides in these cells. Di- and tripeptides that are filtered at the glomerulus, as well as those that are produced in the tubular lumen from larger polypeptides by the action of brush-border peptidases, serve as substrates for the renal peptide transport system under physiological conditions. The H+ gradient that is necessary to drive renal peptide transport is generated in vivo by concerted action of the basolateral Na+-K+-ATPase and the brush-border Na+-H+ exchanger. The peptidases and the peptide transport system in the renal brush-border membrane play a significant role in the reabsorption of peptide-bound amino acids as well as in the regulation of plasma levels of small peptides.
mesh_terms: D000042:Absorption; D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism*; D008954:Models, Biological; D010447:Peptide Hydrolases / Q000378:metabolism; D010455:Peptides / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D010455:Peptides; D010447:Peptide Hydrolases