AJP - Renal Physiology, Vol 251, Issue 6 945-F953, Copyright © 1986 by American Physiological Society
Carrier-mediated reabsorption of small peptides in renal proximal tubule
V. Ganapathy and F. H. Leibach
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.
