Competitive studies relating to tryptophan binding to rat hepatic nuclear envelopes as a sensitive assay for unknown compounds.
Our laboratory has reported that L-tryptophan binds to a rat liver nuclear envelope protein and this binding is saturable, stereospecific and of high affinity. Utilizing an in vitro [3H]tryptophan binding assay to hepatic nuclear envelopes, we have determined the effects of using excess unlabeled L-tryptophan from a number of different suppliers. This study reports that, based on our in vitro binding assay, some significant differences were observed when implicated L-tryptophan in cases of the eosinophilia-myalgia syndrome obtained from a Japanese manufacturer, Showa Denko, was assayed, in contrast to non-implicated L-tryptophan from other suppliers. An isolated impurity of Showa Denko L-tryptophan, 1,1'-ethylidenebis(tryptophan) alone or together with non-implicated L-tryptophan or its breakdown product, 1-methyl-1,2,3,4-tetrahydro-beta-carboline-3-carboxylic acid, did not appreciably affect the in vitro [3H]tryptophan binding to hepatic nuclear envelopes as did the Showa Denko L-tryptophan. Our data, derived with our in vitro binding assay system, suggests that implicated L-tryptophan from Showa Denko contains a compound/s (unknown at present) other than 1,1'-ethylidenebis(tryptophan), which alters in vitro [3H]tryptophan binding. The significance of the impurity/ies involved remains to be determined.
Sidransky
H
H
Department of Pathology, George Washington University Medical Center, Washington, DC 20037.
Verney
E
E
Cosgrove
J W
JW
D000818:Animals; D001667:Binding, Competitive; D004340:Drug Contamination; D005260:Female; D066298:In Vitro Techniques; D008099:Liver / Q000378:metabolism*; D009685:Nuclear Envelope / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D014364:Tryptophan / Q000032:analysis / Q000378:metabolism*
D014364:Tryptophan