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The role of l ‐tryptophan transport in l ‐tryptophan degradation by indoleamine 2,3‐dioxygenase in human placental explants
Author(s) -
Kudo Yoshiki,
Boyd C. A. R.
Publication year - 2001
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.2001.0417i.x
Subject(s) - indoleamine 2,3 dioxygenase , tryptophan , explant culture , biochemistry , chemistry , kynurenine , biology , in vitro , microbiology and biotechnology , amino acid
1 The physiological importance of l ‐tryptophan transport for placental indoleamine 2,3‐dioxygenase‐mediated degradation of l ‐tryptophan has been studied using human placental chorionic villous explants. 2 l ‐Tryptophan influx into villous explants is supported exclusively by transport system L and is substantially inhibited by the L‐system‐specific substrate 2‐aminobicyclo‐(2,2,1)‐heptane‐2‐carboxylic acid (BCH) and also by 1‐methyl‐tryptophan which is also an inhibitor of indoleamine 2,3‐dioxygenase. l ‐Tryptophan influx is enhanced 2.3‐fold following in vitro culture of the villous explant. Interferon‐γ, which increases villous explant indoleamine 2,3‐dioxygenase expression, has no effect on l ‐tryptophan influx. 3 In explants both BCH and 1‐methyl‐tryptophan inhibit indoleamine 2,3‐dioxygenase‐mediated l ‐tryptophan degradation. This also applies when l ‐tryptophan degradation has been stimulated by interferon‐γ. 4 These findings show transport of l ‐tryptophan into the trophoblast to be a rate‐limiting step for indoleamine 2,3‐dioxygenase‐mediated l ‐tryptophan degradation and therefore for the normal physiology of mammalian pregnancy.