Degradation of fluorescent substances derived from malondialdehyde and amino compounds in rat liver microsomes

Abstract

The degradation of fluorescent substances, N-substituted-1, 4-dihydropyridine-3, 5-dialdehyde derivatives, derived from the reaction of malondialdehyde (MDA) which is one of end -degradative products during lipid peroxidation with various amino compounds, was studied in rat liver microsomal fractions. The fluorescent substances from the reaction of MDA with 1-amonopentane, 1-aminoheptane, 1-aminodecane and phenylethylamine (PEA) rapidly changed into water soluble compounds. On the other hand, the fluorescent compounds from short-length amino compounds such as methyl or ethylamine had a little or no change. The degradation system required nicotineamide adenine dinucleotide phosphate, and was inhibited by CO. Furthermore, in microsomal fractions from phenobarbital-pretreated rats, the rate of degradation increased. The degradative compounds of the fluorescent substance from MDA with 14C-phenylethylamine were separated by high performance liquid chromatography. Two major water soluble fluorescent compounds, 4-methyl-1, 4-dihydropyridine-3, 5-dialdehyde (WM-1) and 1-phenylethyl-4-hydroxy-4-methyl-1, 4-dihydropyridine-3, 5-dialdehyde (WM-2), and two minor fat soluble fluorescent compounds were isolated. All of these isolated degradative compounds retained 1, 4-dihydropyridine structure, and exhibited also the same maximum excitation and emission spectra at 392 and 448 nm, respectively, as those of native fluorescent substance. The present results suggested that the microsomal degradation of fluorescent substances related to MDA was dependent on the structure of N-alkyl sidechain of amino compounds.