Parameters of branched-chain amino acids (BCAA; leucine, isoleucine and valine) and protein metabolism were evaluated using L-[1-14C]leucine and a-keto[1-14C]isocaproate (KIC) in the whole body and in isolated perfused liver (IPL) of rats fed ad libitum or starved for 3 days. Starvation caused a significant increase in plasma BCAA levels and a decrease in leucine appearance from proteolysis, leucine incorporation into body proteins, leucine oxidation, leucine-oxidized fraction, and leucine clearance. Protein synthesis decreased significantly in skeletal muscle and the liver. There were no significant differences in leucine and KIC oxidation by IPL. In starved animals, a significant increase in net release of BCAA and tyrosine by IPL was observed, while the effect on other amino acids was non-significant. We conclude that the protein-sparing phase of uncomplicated starvation is associated with decreased whole-body proteolysis, protein synthesis, branched-chain amino acid (BCAA) oxidation, and BCAA clearance. The increase in plasma BCAA levels in starved animals results in part from decreased BCAA catabolism, particularly in heart and skeletal muscles, and from a net release of BCAA by the hepatic tissue., M. Holeček, L. Šprongl, I. Tilšer., and Obsahuje bibliografii
Rats received an injection of [14C]leucine and were then divided into four groups. Groups I and II consisted of ad libitum fed rats were administered saline or endotoxin of Salmonella enteritidis eight and twenty-two h after the [14C]leucine treatment. Animals of Group III (saline) and Group IV (endotoxin) fasted after [14C]leucine injection. Twenty three hours after [14C]leucine treatment rats were injected with pHjleucine and sacrificed 20 min afterwards. Endotoxin administration decreased body weight in fed rats only. After endotoxin treatment, higher [3H]leucine specific activity in the blood plasma, decreased leucine incorporation into proteins and lowered plasma amino acid levels were observed. [14C]leucine radioactivity was significantly higher in the spleen and lower in skeletal muscles of endotoxin-treated rats. All changes were less expressed in fasted than in ad libitum fed animals. Our results indicate that endotoxin treatment results in (a) changes in host metabolism that are not mediated solely by anorexia; (b) a decrease of protein synthesis in the viscera and skeletal muscles; (c) an increase of protein degradation in skeletal muscles; (d) reutilization of leucine released from skeletal muscles in viscera, and (e) a slower disappearance rate of leucine from the blood.