Serum amino acids in experimentally induced endotoxic shock: the prognostic significance of hyperalaninemia.
Serum amino acid levels were determined in 40 male rabbits before and 2, 6, and 24 hr after shock induction with 50 micrograms kg-1 endotoxin from Escherichia coli 0 111 and compared with amino acid levels of 32 age-matched control animals. Whereas total amino acid concentration in the control group decreased continuously over the 24 hr period due to fasting of the animals, the corresponding concentration in the endotoxin-treated animals remained at the initial level for the first 6 hr after shock induction. During this period, the release of amino acids from peripheral tissues was apparently enhanced, as evidenced by elevated levels of serum phenylalanine and tyrosine. Endotoxin administration exerted a salient effect on serum alanine levels. In all endotoxin-treated rabbits, alanine concentration was increased significantly 2 hr (P less than 0.00001) and 6 hr (P less than 0.00001) after injection of the toxin, whereas alanine levels in the control group remained essentially unchanged. In most animals, peak alanine concentrations were observed at the 6 hr sampling time. Blood glucose measurements indicated that by this time the hyperglycemic period, which is typical of the initial phase of endotoxic shock, was already finished. A high level of alanine following shock induction alluded to the impending death of the animal. In all rabbits in which alanine concentration rose by more than 600 mumols l-1 during the first 2 hr after endotoxin administration, the increase correlated significantly with the rate of lethality (P less than 0.0001). In contrast, alanine levels of surviving animals increased only moderately. It was concluded from these results that monitoring serum alanine levels might be a valuable and practical tool to assess the severity and outcome of endotoxic shock.