Amino acid disposition by liver and gastrointestinal tract after protein and glucose ingestion.

Hepatic uptake and gut and splanchnic output of amino acids were determined after administration of protein and glucose loads in conscious dogs with indwelling catheters in the femoral artery and portal and hepatic veins. Oral or parenteral glucose given with a beef meal blunted the rise in arterial amino acids relative to that seen with ingestion of beef alone. Gut amino acid output was considerably delayed with oral hypertonic glucose, but was unchanged with parenteral glucose and with oral isotonic glucose. Ingestion of beef with oral hypertonic mannitol, a nonabsorbable sugar alcohol, delayed the rise in gut amino acid output in a manner similar to that seen with beef plus oral hypertonic glucose. We have evaluated the relationship between circulating amino acids, circulating hormone concentrations, and amino acid metabolism. Significant correlations with hepatic amino acid uptake were found for insulin, for arterial and portal amino acid levels, and for gut amino acid output. Partial correlation analysis suggests that gut amino acid output is the major determinant of hepatic amino acid uptake.