STUDIES WITH 1,1'-ETHYLIDENEBIS(TRYPTOPHAN), A CONTAMINANT ASSOCIATEDWITH L-TRYPTOPHAN IMPLICATED IN THE EOSINOPHILIA-MYALGIA-SYNDROME

L-Tryptophan binds to a rat liver nuclear envelope protein, and this b inding is saturable, stereospecific, and of high affinity. Utilizing a n in vitro assay of [H-3]tryptophan binding to rat hepatic nuclear env elopes, we have previously determined that the L-tryptophan obtained f rom Showa Denko and which was implicated in cases of the eosinophilia- myalgia syndrome (EMS) inhibited [H-3]tryptophan binding differently t han did control L-tryptophan (not implicated in EMS). Therefore, in th is study we investigated whether the addition of 1,1'-ethylidenebis(tr yptophan) (EBT), a contaminant or impurity in L-tryptophan implicated in EMS, would have an effect. Our results indicate that EBT alone has little inhibitory binding effect compared with that of control L-trypt ophan and that when EBT was added to control L-tryptophan the inhibito ry binding effort was similar to that of control L-tryptophan alone. O n the other hand, in vitro addition of EBT plus L-tryptophan to nuclei of cultured murine macrophages (WLG5) results in less inhibition of [ H-3]-tryptophan binding than does addition of L-tryptophan alone. Simi lar in vitro additions to nuclei of rat brain reveal little effect on binding, as was also the case for hepatic nuclear envelopes. Adding EB T to an in vitro hepatic protein synthesis system and measuring [H-3]t ryptophan incorporation into acid-precipitable proteins reveal that it competes similarly to that found with equimolar concentrations of unl abeled L-tryptophan. It does not affect [C-14]leucine incorporation in to proteins. [C-14]EBT becomes incorporated in vitro into proteins (ac id-precipitable), and this incorporation is diminished in the presence of equimolar concentrations of unlabeled EBT or L-tryptophan. This su ggests that EBT or possibly a breakdown product becomes incorporated i nto proteins. Speculation as to how EBT may affect tissues in experime ntal animals is presented. (C) 1994 Academic Press, Inc.