[Renal excretion of xanthurenic acid as an index of vitamin B6 allowance in infants].

Renal excretion of xanthurenic acid without any tryptophan load, passage of 4-pyridoxic acid with diurnal urine and its excretion with urine collected during 1 hour in the morning on an empty stomach were investigated in 86 practically healthy infants and in 77 others with acute respiratory viral infections aged from two weeks to one year. Investigations of the tryptophan tolerance in infants yielded negative results, viz. on administering to them of D,L-tryptophan in a load dose the infants started vomiting. Practically healthy infants did not excrete xanthurenic acid, while the renal excretion of 4-pyridoxic acid remained within normal limits. In patients at the height of the disease the passage of 4-pyridoxic acid steeply increased. In 9 of them xanthurenic acid appeared in the diurnal urine. In the quiscent stage of the affection in two infants xanthurenuria continued against the general background of diminished excretion of 4-pyridoxic acid. There is no reason to relate the disclosed xanthurenuria in sick infants with the state of hypovitaminosis in them.