AJP - Endocrinology and Metabolism, Vol 243, Issue 5 413-E417, Copyright © 1982 by American Physiological Society
Enrichment of glycine pool in plasma and tissues by glycine, di-, tri-, and tetraglycine
S. A. Adibi and E. L. Morse
Very little information is available on metabolism of oligopeptides in
vivo. The present studies were performed to investigate the metabolic fate
of diglycine, triglycine, and tetraglycine when injected into a central
vein in rats. These peptides disappeared rapidly from plasma without any
significant loss in urine. Plasma and tissue concentrations of glycine were
measured when the same amount of glycine was injected in free or peptide
form. Two minutes after the injection of glycine (1.l0 mumol/g body wt),
there was over a tenfold increase in plasma glycine concentration. This
increase was diminished when diglycine instead of glycine was injected.
Each increase in the number of glycine residues resulted in further
reduction in the initial rise in plasma glycine concentration was increased
by each injection. This was more pronounced in the kidney than in the
liver. Injection of triglycine and tetraglycine resulted in greater glycine
concentration in the kidney than injection of either glycine or diglycine.
Furthermore, unlike liver and muscle, each increase in the number of
glycine residues resulted in greater recovery of glycine peptides from the
kidney. These results suggest that with each increase in the number of
glycine residues a greater amount of injected glycine peptide is taken up
by the kidney for hydrolysis to glycine.
