Leucine and glutamine metabolism in septic rats

The rate of leucine C-2 incorporation into glutamine was compared in control and septic rats. Female Sprague-Dawley rats (n = 46, 210-260 g) were fed parenterally for 3 days and then randomized into two groups (control and septic). Sepsis was induced by the injection of 10¹⁰ live Escherichia coli/kg on day 4 into the septic group. Rats in each group were given a continuous (8 h) infusion of one of three different isotopes. The isotopes were given 24 h after inoculation. Leucine oxidation and incorporation into protein were determined with [1-¹³C]leucine; glutamine flux and oxidation were determined with [5-¹³C]glutamine, and the fraction of leucine C-2 incorporated into glutamine was determined by giving [1,2-¹³C]leucine. Results were as follows: sepsis caused a significant increase in the rate of leucine C-2 incorporation into glutamine (66.0±3.7 as against 29.6±3.7 μmol/h per kg, P < 0.01). This increase was due to both an increase in glutamine production (2331±76 as against 1959±94 μmol/h per kg, P < 0.01) and an increase in the proportion of glutamine derived from leucine(2.83±0.27% as against 1.51±0.31%, P < 0.01). The ratio of leucine C-2 incorporated into glutamine to leucine oxidized increased from 7.16±0.91% to 11.49±1.12% with sepsis (P < 0.05).