Metabolism of glycylleucine and its constituent amino acids by liver, muscle, kidney and gut in conscious dogs.

The role of liver, muscle, kidney and gut in the assimilation of intravenously administered glycylleucine was investigated in 8 mongrel dogs. The rates of disappearance of glycylleucine during its passage across liver, muscle, kidney and gut were 1487 +/- 80, 740 +/- 216, 1436 +/- 115, and 602 +/- 103 mumol/(min x kg B.W.), respectively. The infusion of glycylleucine greatly altered the fluxes of glycine and leucine across these organs. The major alterations included increases in the uptake of glycine by the liver and that of leucine by the muscle, and increases in release of leucine by liver and kidney. We conclude that all organs are involved in the assimilation of intravenously administered glycylleucine, but with varying importance. Although liver and kidney appear to be the dominant organs for the assimilation of glycylleucine, the metabolism of glycine is chiefly accomplished in the liver, and that of leucine is chiefly accomplished in the muscle.