Metabolism of tetraglycine in isolated non-filtering rat kidneys

: The purpose of this work was to study the metabolism of tetraglycine in the isolated non filtering rat kidney. Kidneys were perfused with Krebs-Henseleit solution containing 1 mM of tetraglycine. The determination of the peptidic residues and their components was done in an aminoacid microanalyzer. The results showed that tetraglycine was significantly oxidized to a maximal concentration of 0.12 mM at the end of 120 minutes (88%). The peptide was degraded to its constituents, diglycine and glycine. There was no elution of triglycine. The tetrapeptide produced glycine in increasing concentrations while diglycine as a metabolite was almost constant up to 80 minutes of perfusion. The hydrolysis of tetraglycine allowed us to believe that aminopeptidase, carboxypeptidase and dipeptidyl dipeptidase can be present in the contraluminal membranes of the rat kidney contributing to the handling of tetraglycine. Our results indicate newer pathways of the tetrapeptide metabolism.