A. DeCaprio, E. Olajos, P. Weber
Sep 30, 1982
Citations
1
Influential Citations
129
Citations
Quality indicators
Journal
Toxicology and applied pharmacology
Abstract
Abstract The industrial solvents n -hexane and methyl n -butyl ketone are metabolized to the neurotoxic γ-diketone 2,5-hexanedione (2,5-HD) in several species, including man. Other γ-diketones are also neurotoxic, while α- and β-diketones are not. The γ-diketones are believed to directly interact with axonal components, possibly by covalent binding. Experiments were designed to evaluate the formation of 2,5-disubstituted pyrrole adducts by the reaction of γ-diketones with primary amines, a scheme which could account for both the structure/activity requirements and covalent binding. Incubation of primary amines with 2,5-HD under physiologic conditions (pH = 7.4, T = 37° C ) caused extensive substituted pyrrole formation, a result which was also extended to other γ-diketones. The β-diketone 2,4-hexanedione also reacted with amino groups, but without formation of pyrroles. Structure of the pyrrole derivative was confirmed by mass and iR spectroscopy. Similar in vitro experiments with proteins demonstrated conversion of lysine ∈-amino groups to 2,5-dimethylpyrrole adducts by 2,5-HD, with the degree of conversion directly proportional to the lysine content of the protein. Polyacrylamide gel electrophoresis of 2,4- and 2,5-HD-treated proteins revealed progressive loss of positive charge, consistent with binding to lysine ∈-amino groups. Protein exposed to 2,5-HD became pyrrole positive. The formation of orange (λ max = 475 nm) chromophores in γ-diketone:amine mixtures was attributed to a secondary oxidation of the initially formed pyrrole reaction product. HPLC analysis of protein hydrolysates demonstrated pyrrole adduct formation in both protein exposed to 2,5-HD in vitro and in serum protien from hens given daily, po doses of 200 mg 2,5-HD/kg for 2 weeks. The results suggest pyrrole formation as the probable mode of in vivo tissue binding of 2,5-hexanedione.