Identification of crotonaldehyde as a hepatic microsomal metabolite formed by alpha-hydroxylation of the carcinogen N-nitrosopyrrolidine.
Crotonaldehyde (2-butenal), which reacts with DNA and is mutagenic and carcinogenic, was identified as a hepatic microsomal metabolite of the hepatocarcinogen N-nitrosopyrrolidine. Incubation mixtures of N-nitrosopyrrolidine, cofactors, and hepatic microsomes from Aroclor pretreated or control F344 rats were derivatized with (2,4-dinitrophenyl)hydrazine reagent and the resulting mixtures analyzed by high-performance liquid chromatography. Crotonaldehyde (2,4-dinitrophenyl)hydrazone was identified by its retention time in two different systems and by its ultraviolet and mass spectrum. The ratio of 4-hydroxybutyraldehyde, which has previously been identified as a metabolite of NPYR, to crotonaldehyde was 1.5-2 over a range of substrate concentrations. The approximate values of Km and nu max for crotonaldehyde were 5.8 mM and 0.6 nmol/min/mg of protein and for 4-hydroxybutyraldehyde 14.1 mM and 1.7 nmol/min/mg of protein, for substrate concentrations between 1 and 8 mM, with microsomes from Aroclor pretreated rats. The ratio of 4-hydroxybutyraldehyde to crotonaldehyde was 1.9 upon esterase-catalyzed solvolysis of alpha-acetoxy-N-nitrosopyrrolidine, a stable precursor to the initial product of N-nitrosopyrrolidine alpha-hydroxylation. These results demonstrate that crotonaldehyde is formed upon metabolic alpha-hydroxylation of N-nitrosopyrrolidine and suggest that it may be involved in N-nitrosopyrrolidine-macromolecule interactions.
Wang
M Y
MY
Division of Chemical Carcinogenesis, American Health Foundation, Valhalla, New York 10595.
Chung
F L
FL
Hecht
S S
SS
D000447:Aldehydes / Q000302:isolation & purification / Q000378:metabolism*; D000818:Animals; D001711:Biotransformation; D002851:Chromatography, High Pressure Liquid; D006900:Hydroxylation; D007700:Kinetics; D008297:Male; D008862:Microsomes, Liver / Q000378:metabolism*; D009242:N-Nitrosopyrrolidine / Q000378:metabolism*; D051381:Rats; D011916:Rats, Inbred F344
D000447:Aldehydes; C012796:2-butenal; D009242:N-Nitrosopyrrolidine