TABLE 2.

Names and abbreviations used for variables

In equations	In text	Full name
trp	tryptophan	Free tryptophan in liver
nfk	NFK	N-formyl-kynurenine
kyn	Kyn	Kynurenine
Ka	KA	Kynurenic acid
aa	AA	Anthranilic acid
hk	HK	3-Hydroxykynurenine
xa	XA	Xanthurenic acid
haa	HaA	3-Hydroxyanthranilic acid
qa	QA	Quinolinic acid
portrp	portrp	Tryptophan in the portal circulation
lpool	Lpool	Tryptophan incorporated into proteins in liver
mtrp	Mtrp	Free tryptophan in muscle
mpool	Mpool	Tryptophan incorporated into proteins in muscle
pertrp	pertrp	Tryptophan in the peripheral circulation
gtrp	gtrp	Tryptophan in the gut