Abstract
Urinary indoleacetic acid (IA) has been thought to be derived from the conver-sion of tryptophan to IA through the action of both intestinal bacteria and tissue enzymes. There has been, however, no direct evidence of the In vivo conversion of tryptophan to IA by tissue enzymes. The present studies were made to elucidate this question. Intravenous loading of tryptophan to three children revealed a remarkable increase in IA excretion into urine. Consecutive administration of chloramphenicol resulted in a decrease in IA excretion but was unable to eliminate urinary IA. Increase in IA excretion following oral tryptophan loading during chloramphenicol treatment was found to correspond approximately to that fol-lowing the intravenous tryptophan loading on the same dosis. These results give us a direct evidence of the In vivo conversion of tryptophan to IA by tissue enzymes.
