Effect of Copper Status on the Urinary Excretion of Tryptophan Metabolites and Amino Acids by the Rat

Abstract

The effect of dietary copper on selected metabolic systems requiring pyridoxal phosphate was investigated by comparing certain urinary excretory products of pair-fed copper-deficient and copper-adequate rats. Kynurenic acid and xanthurenic acid, two tryptophan metabolites, were in lower concentrations in the urines of the copper-deficient animals in the pretryptophan-load period. Following a tryptophan load, these metabolites increased markedly in the urines of both groups, but the in crements were much larger for the copper-deficient animals. The increases in kynurenic acid were greater than those of xanthurenic acid in both groups, but the increase was disproportionately higher in the copper-deficient rats. The excretion of taurine and urea by the copper-deficient rats was significantly less. At the dilution used, several amino acids were found in significant amounts in the urines of the copper-deficient animals, whereas only taurine was detected in the urines of those fed copper. Several possible explanations of these findings are discussed. J. Nutr. 103: 1764-1771, 1973. INDEXING KEYWORDS urinary amino acids •ure copper deficiency •urinary tryptophan metabolites