Effect of supplementation of methionine and threonine to a protein free diet on urinary excretion of nitrogen and tissue free amino acids in rats
Yokogoshi, H.; Hayase, K.; Yoshida, A.
Journal of Nutrition 107(5): 783-791
1977
ISSN/ISBN: 0022-3166 PMID: 870649 Document Number: 122136
Young male Wistar rats weighing 100-120 g were fed for 10 days on a protein-free diet without or with added L-methionine 0.3% and L-threonine 0.3%. Urine was collected for the last 3 days for estimation of urea and N. After blood had been collected by cardiac puncture the rats were killed and the liver was removed for chemical analysis. In the 2nd experiment the effect of supplementary methionine and threonine on the concentration of free amino acids in plasma and intestines was studied in male rats. The 3rd experiment dealt with the effect of the supplements on concentrations of NH3, urea and free amino acids in plasma of female rats. The effects of the supplements on plasma ornithine were also studied.The urinary loss of N in rats fed on the protein-free diet was significantly greater than that of rats given the amino acid supplemented diet; the same was true for urinary and plasma urea. NH3 in plasma was similar in the 2 groups. In the liver the concentration of free amino acids was less with the supplemented diet; in the intestine free amino acids were not significantly different in the dietary groups. In female rats the relative liver weights of rats given the amino acid-supplemented diet were slightly greater than those of rats on the protein-free diet alone. Values for plasma urea and NH3 and of liver free amino acids paralleled those in male rats. The concentration of ornithine in liver was less with the supplemented diet. The findings suggest that the decreased migration of free amino acids from peripheral tissues to liver and the decreased concentration of ornithine in liver reduce urea formation in rats fed on the diet supplemented with methionine and threonine.