Tryptophan supplementation significantly decreased expression of Ahrr, but increased expression of Cyp1a1, Arnt, and Tiparp. Maternal CKD had a negligible effect on most AHR target genes, except there was a lower renal mRNA expression of Ahrr in the CKD and CKDTrp groups vs. controls. The gene discussed is AHR; the disease is chronic kidney disease.