Alterations in Plasma Amino Acid Homeostasis During Experimental Endotoxemia.

Abstract : Studies were performed in rats to determine the effect of endotoxin administration on individual plasma free amino acid concentrations since altered amino acid homeostasis could be involved in pathophysiologic mechanisms during endotoxemia. Intraperitoneal administration of Salmonella typhimurium endotoxin (1.0 mg/100 g body weight) induces an early and persistent hypertaurinemia, hyperglucagonemia as well as transient hyperinsulinemia and a generalized hypoaminoacidemia during a 5-h experimental period. Depressions in plasma concentrations of most amino acids appear to be attributable to endotoxin-induced elevations in peripheral glucagon and ureagenesis. Arginine nearly disappeared from plasma within 3 h and was not detectable by 5 h. Marked alteration in arginine concentration may be due, in part, to hyperglucagonemia and the liberation of intracellular arginase from various tissues and its enhanced activity in peripheral blood. Overt hepatocellular damage was detectable by 3 h and may contribute to altered plasma glucose and amino acid homeostasis during the latter stages of endotoxicosis. Hypertaurinemia was demonstrable with a wide range of endotoxin doses (0.05-1 mg). Early hypertaurinemia may result as a consequence of destruction of formed elements of the blood, whereas the sustained condition may involve more complex mechanisms.