Hemoglobin Binding of Bicyclic Aromatic Amines

Abstract

Aromatic diamino compounds, e.g., 4,4'-methylenebis(2-chloroaniline) (MOCA) and 4,4'-methylenedianiline (MDA), are used as curing agents in the production of elastomers. Since MOCA and MDA are mutagenic and carcinogenic, substitutes are of great commercial interest. For benzidine it has been shown that ortho substitution with methyl groups yields the nonmutagenic 3,3',5,5'-tetramethylbenzidine. Therefore, MDA analogues with large substituents in the ortho position have been synthesized. The substituents are supposed to inhibit the formation of the N-hydroxyarylamines which are the putative genotoxic intermediates. We investigated the biological availability of the N-hydroxylamines of ortho-substituted diamines and of known carcinogenic diamines in female Wistar rats, by determining hemoglobin (Hb) adducts. Hb from rats dosed with 0.5 mmol/kg diamine and from controls was isolated and hydrolyzed in base. The released diamine and monoacetyldiamine were quantified by HPLC with electrochemical detection and/or GC/MS. MDA, 4,4'-oxydianiline (ODA), 4,4'-ethylenedianiline, and 4,4'-thiodianiline (TDA) bound to hemoglobin as diamine and as monoacetyl-diamine. 4,4'-Methylenebis(2,6-dimethylaniline), 4,4'-methylenebis(2,6-diethylaniline), MOCA, and 4,4'-sulfonyldianiline (dapsone) bound only as diamine to Hb. 4,4'-Methylenebis(2,6-dichloroaniline) did not bind to Hb. Thus, the presence of two substituents in the ortho position and the presence of electron-withdrawing groups in the para position to the amino group drastically reduced the formation of Hb adducts. The amount of hemoglobin adducts was compared to their carcinogenic potency. The extent of hemoglobin binding of the bicyclic diamines (dapsone, 3,3'-dichlorobenzidine, MDA, MOCA, TDA, ODA, and benzidine) increases with their carcinogenic potency.

Critical analysis of biomonitoring endpoints for measuring exposure to polymeric diphenyl-methane-4,4'-diisocyanate (MDI) in rats: a comparison of markers of exposure and markers of effect

“…This tentative pathway for formation of haemoglobin adducts requires neither the formation of free amines nor an extrapulmonary activation as previously suggested (Sepai et al 1995a;Sabbioni and SchuÈ tze 1998;Sabbioni et al 2000). The haemoglobin binding index (HBI = molecular adducts of compound/gHb : molecular compound/kg body weight), as proposed by Sabbioni and SchuÈ tze (1998), for total MDA was 3 and 0.04 after oral dosing with MDA and MDI, respectively (Sabbioni and SchuÈ tze 1998). The HBI found in this study for the respirable aerosol of monomeric MDI was 0.000017, and for total inhalable MDI ten-fold lower.…”

Analysis of biomarkers in rats and dogs exposed to polymeric methylenediphenyl diisocyanate (pMDI) and its glutathione adduct

“…Previous inhalation studies in rats with aerosols of MDA and pMDI resulted in ratios of 2 and 4-6, respectively, whilst in epicutaneously pMDI-exposed rats ratios from 8-15 were observed (Pauluhn and Lewalter, 2002). In rat experiments with MDA the ratio of AcMDA/MDA shifts in favor to AcMDA at lower doses (range 3-11) as reported by Sabbioni and Schütze (1998). Thus, the diagnostic value of any differentiation of AcMDA and MDA related hemoglobin adducts cannot be judged conclusively.…”

Electrochemical Oxidation of Prednisolone at Glassy Carbon Electrode and Its Quantitative Determination in Human Serum and Tablets by Osteryoung Square Wave Voltammetry

“…Furthermore, LC/MS has been applied to the studies of the reaction between mutagens and proteins [97][98][99][100][101][102][103].…”