Tryptophan deficiency and picolinic acid: effect on zinc metabolism and clinical manifestations of pellagra.
In five experiments, rats were fed tryptophan (Tryp)-deficient diets with 6-12 micrograms/g zinc (Zn) and, in one experiment, a Zn-deficient diet to test the effect on clinical manifestations, plasma and bone Zn, and ability of picolinic acid (PA) or extra (12 micrograms/g) Zn to compensate. Tryp deficiency caused classical manifestations of pellagra although niacin intake was in excess of normal requirements. At marginal Zn intakes, oral PA caused a significant increase of plasma Zn and, compared with Tryp-adequate controls, Tryp deficiency resulted in lower plasma Zn and plasma:bone Zn ratios. Extra Zn (total 24 micrograms/g) was ineffective. Subcutaneous PA showed a tendency to lower plasma Zn. PA had no effect on clinical manifestations. We conclude that a Tryp metabolite other than nicotinic acid is necessary in the prevention of pellagra. Our hypothesis links this finding with the observed Tryp and PA effect on Zn metabolism.
D000818:Animals; D001835:Body Weight; D001842:Bone and Bones / Q000378:metabolism; D004032:Diet; D008297:Male; D010383:Pellagra / Q000209:etiology* / Q000517:prevention & control; D010848:Picolinic Acids / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D014018:Tissue Distribution; D014364:Tryptophan / Q000172:deficiency*; D015032:Zinc / Q000378:metabolism* / Q000502:physiology
D010848:Picolinic Acids; D014364:Tryptophan; D015032:Zinc; C030614:picolinic acid