Document Detail


Synthesis, characterization, and solvolysis of mono- and bis-S-(glutathionyl) adducts of methylene-bis-(phenylisocyanate) (MDI).
MedLine Citation:
PMID:  12387619     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
Bifunctional isocyanates are highly reactive compounds that undergo nucleophilic attack by a variety of functional groups available in the biological system. While the etiology of the respiratory disease caused by diisocyanates is not fully understood, a great deal of research has been performed to elucidate the chemical mechanisms involved in the direct and indirect effects of these compounds. Since adducts of isocyanates are found not only to proteins along the entire respiratory tree but also to proteins in the circulatory system, it is likely that a transport mechanism for the isocyanate from the respiratory to the circulatory system exists. The initial reaction of isocyanates with cellular thiols to form thiocarbamates, which are known to release the isocyanate under physiological conditions, is believed to provide a possible carrier mechanism for the isocyanate functional group. Previous work with aliphatic mono-isocyanates and the aromatic diisocyanate toluene diisocyanate has demonstrated the feasibility of this mechanism. Adding to this database, the products of the reaction of the highly water-insoluble, low vapor pressure, methylene-bis-(phenylisocyanate) (MDI) with glutathione were synthesized, and their chemical stability under various pH and buffer conditions was tested. Novel synthetic routes were developed for both the mono- and bis-S-(glutathionyl) adducts with MDI that yielded each compound in analytically pure form. Both compounds were found to be unstable under mild basic conditions (phosphate-buffered saline, pH 7.4, and NaHCO(3), pH 8.2), however to a different degree. Furthermore, a significant influence of the pH value (the rate of degradation increases with pH) and the concentration of free glutathione (increasing thiol stabilizes the adduct) on the stability was observed, indicating a base-catalyzed mechanism of the degradation/formation of the thiocarbamate bond. Unlike the monoadduct, which forms almost exclusively the polyurea upon degradation, a variety of products were formed upon degradation of the bis adduct. Though the disappearance of the bis adduct was complete as measured by HPLC, (1)H NMR spectra showed the existence of residual thiocarbamate bonds in the final mixture. In both cases, no evidence of the free methylene-bis-phenylamine (MDA) could be detected under the applicable conditions.
Authors:
Martin Reisser; Brigitte F Schmidt; William E Brown
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Publication Detail:
Type:  Journal Article; Research Support, U.S. Gov't, Non-P.H.S.    
Journal Detail:
Title:  Chemical research in toxicology     Volume:  15     ISSN:  0893-228X     ISO Abbreviation:  Chem. Res. Toxicol.     Publication Date:  2002 Oct 
Date Detail:
Created Date:  2002-10-21     Completed Date:  2003-04-17     Revised Date:  2006-11-15    
Medline Journal Info:
Nlm Unique ID:  8807448     Medline TA:  Chem Res Toxicol     Country:  United States    
Other Details:
Languages:  eng     Pagination:  1235-41     Citation Subset:  IM    
Affiliation:
Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, USA.
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MeSH Terms
Descriptor/Qualifier:
Allergens / chemistry,  metabolism*
Chromatography, High Pressure Liquid
Glutathione / chemistry*,  metabolism
Humans
Hydrogen-Ion Concentration
Isocyanates / chemical synthesis,  chemistry,  metabolism*
Magnetic Resonance Spectroscopy
Respiratory Tract Diseases
Chemical
Reg. No./Substance:
0/Allergens; 0/Isocyanates; 101-68-8/4,4'-diphenylmethane diisocyanate; 70-18-8/Glutathione

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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