Endotoxin and renal glutamine metabolism
T. R. Austgen, M. K. Chen, W. Moore and W. W. Souba
Department of Surgery, University of Florida College of Medicine, Gainesville 32610.
The effect of endotoxin on renal glutamine metabolism and ammoniagenesis
was investigated in vivo in the rat to gain further insight into the
altered glutamine flow that characterizes critical illness. Studies were
done 15 hours following a single dose of Escherichia coli
lipopolysaccharide (10 mg/kg). Renal blood flow and arterial glutamine
concentration were similar in control and study rats, but the kidney
switched from an organ of slight glutamine uptake in controls (129 +/- 52
nmol/100 g of body weight per minute) to net release in the
endotoxin-treated animals (-273 +/- 170 nmol/100 g of body weight per
minute). Simultaneously, the specific activity of renal glutamine
synthetase increased by almost 50% (374 +/- 40 nmol/mg of protein per hour
in rats given endotoxin vs 253 +/- 12 nmol/mg of protein per hour in
controls), while glutaminase was unchanged. Urinary ammonia excretion was
reduced by 35% in the endotoxin-treated animals (47 +/- 6 mumol/12 h in
endotoxin-treated animals vs 70 +/- 8 mumol/12 h in controls) despite a 10%
fall in the arterial bicarbonate value. Endotoxin alters the net flux of
glutamine across the kidney which appears to be partially regulated
enzymatically. This may impair the kidneys' ability to maintain acid/base
homeostasis.
