Alanine metabolism in the skeletal muscle and plasma in endotoxemia

: Utilizing a 24 hour fasting rabbit (N = 30), we measured free amino acids in the femoral artery and vein and the quadriceps femoris muscle. The endotoxin E. coli 026, 3.0mg/kg (LD100) was injected and free amino acid plasma levels were monitored for 6 hours. Changes in free amino acid plasma levels were variable and marked after endotoxin injection. By 360 min. after endotoxin injection: (a) the rate of increase in free amino acid levels in the femoral artery was 366 mumole/l of alanine, 162 mumole/l of glycine and 85 mumole/l of proline; (b) the rate of increase in free amino acid of the quadriceps femoris muscle was 1376 nmole/g of alanine, 156 nmole/g of glycine and 109 nmole/g of serine; and (c) the femoral arteriovenous difference was -225 nmole/l of alanine, -118 nmole/l of glycine and -77nmole/l of proline. Within 10 min. after endotoxin injection, alanine concentration was higher in the femoral vein. This change in concentration became significant by 60 min. The results show the following: Skeletal muscle appears to be an important source of amino acids for amino acid metabolism during endotoxemia, especially plasma alanine which is closely connected with alanine levels in skeletal muscle.