Plasma Amino Acids in Fed and Fasted Wethers

Abstract

The effect of fasting on plasma amino acids and the half-life estimate for uptake of total plasma radioactivity from C-L-leucine(UL) was studied with 10 wether lambs averaging 46 kg in weight. Blood samples were taken at intervals (0 to 3 hr) starting 4 hr and 24 hr postprandially. Of the essential amino acids, the fasted lambs had overall lower mean plasma concentrations of isoleucine, phenylalanine, valine, leucine, lysine and total essential amino acids than fed lambs. Of the non-essential amino acids, overall mean plasma concentrations of glutamic acid and tyrosine were lower in the fasted animals. Plasma glycine was increased approximately twofold with fasting. Radioactive leucine was removed from plasma of fed and fasted wethers with a mean half-time of 5.7 ± .51 and 6.2 ± .98 min, respectively. The plasma protein of fed and fasted wethers contained 54.4% and 55.5%, respectively, of the total radioactivity at 3 hr after injection of the isotope. It can be concluded from these data that fasting affects plasma concentrations of several free amino acids, however, fasting did not affect the plasma turnover of total radioactivity from ¹⁴C-L-leucine. Radioactive leucine was removed from plasma of fed and fasted wethers rather rapidly, and a considerable amount of the radioactivity later re-entered the plasma in a protein fraction. Copyright © 1975. American Society of Animal Science . Copyright 1975 by American Society of Animal Science.