Two patients with Hartnup disease were studied for tryptophan loading test. The increase in kynurenine and N-methylnicotinamide following the tryptophan loading was less remarkable in the Hartnup patients than in controls. On the other hand, the Hartnup patients revealed a striking elevation of indoleacetic acid and indican following the loading as compared with those in controls. Plasma levels of tryptophan following the loading indicated a lower peak in the Hartnup patients than in controls. These results suggest malabsorption of tryptophan in the intestine.
The in ritro studies on uptake of tryptophan by leukocytes failed to demonstrate a specific defect in transport of tryptopha.n in a Hartnup patient.
Tohoku University Medical Press