The effects of hyperalimentation and infused leucine on the amino acid metabolism in sepsis: an experimental study in vivo.

Liver blood flow and exchange of oxygen, glucose, lactate, and amino acids were measured in pigs at the same time as the peripheral arteriovenous (A-V) difference of these substances was determined. Four groups of animals were studied; they were normal postabsorptive, septic fasted, and septic infused either with complete parenteral nutrition (4.25% mixed amino acid solution with 25% glucose) or an isocaloric solution of 1.8% leucine with glucose. Sepsis in the pig caused a rise in arterial concentration of all essential amino acids except tryptophan and a decrease of most of the others. The liver uptake of the sum of all amino acids rose from nonsignificant values to 26.03 mumol/min/kg at the same time as the peripheral A-V difference changed from +20.4 to -678.0 mumol/l. Hyperalimentation increased arterial amino acid concentration, whereas peripheral A-V difference decreased to -132.3 mumol/l. The total liver uptake of amino acids was 24.80 mumol/min/kg but with a higher proportion of essential amino acids than in the fasted septic state suggesting increased liver protein synthesis. When leucine and glucose were infused the peripheral A-V difference of the sum of all amino acids was only -45.6 mumol/l indicating an almost complete cessation of muscle proteolysis. The arterial plasma concentration of all amino acids except leucine, glutamine, and glutamate were markedly reduced. Although hepatic clearance rate of amino acids fell only slightly, due to the low plasma concentrations, the liver uptake decreased substantially to 7.37 mumol/min/kg suggesting a decreased liver protein synthesis which could be deleterious in the presence of sepsis.