Table 2.

Comparison of AhR agonistic activity induced by Trp and its 15 metabolites.

Compound	REC10 (a)	Relative Potency (b)
TCDD	1.0 × 10−12	1
L-Tryptophan	N.E. (c)	<3.3 × 10−9
L-Kynurenine	7.0 × 10−7	1.4 × 10−6
Tryptamine	6.3 × 10−5	1.6 × 10−8
3-Methylindole	7.8 × 10−5	1.3 × 10−8
Xanthurenic acid	1.2 × 10−4	8.3 × 10−9
5-Hydroxyindole-3-acetic acid	1.5 × 10−4	6.7 × 10−9
Indole-3-carboxylic acid	N.E.	<3.3 × 10−9
Indole-3-carboxaldehyde	N.E.	<3.3 × 10−9
Indole-3-acetamide	N.E.	<3.3 × 10−9
3-Indoleacetic acid	N.E.	<3.3 × 10−9
3-Indolepropionic acid	N.E.	<3.3 × 10−9
Indole	N.E.	<3.3 × 10−9
Kynurenic acid	N.E.	<3.3 × 10−9
Anthranilic acid	N.E.	<3.3 × 10−9
Pyridine-2-carboxylic acid	N.E.	<3.3 × 10−9
2,3-Pyridinedicarboxylic acid	N.E.	<3.3 × 10−9

^(a) 10% relative effective concentration (M): the concentration of the test compound showing 10% of the agonistic activity induced by 1 × 10⁻¹⁰ M TCDD. ^(b) Relative potency is expressed as a ratio of REC10 of TCDD to that of a test compound; i.e., the relative potency of TCDD is arbitrarily set at 1. ^(c) No effect (REC10 > 3 × 10⁻⁴ M).