Metabolism of aromatic and heterocyclic amine bladder carcinogens: bioanalytical considerations.
Aromatic and heterocyclic amines are environmental chemicals which can cause bladder cancer in man. Because these chemicals cause carcinomas at a site distal to their portals of entry, metabolic processes are involved in initiation of their carcinogenic effects. N-[4-(5-nitro-2-furyl)-2-thiazolyl]formamide (FANFT) and its deformylated analogue, ANFT, were used as model compounds to assess metabolism. Electrochemical properties of ANFT made liquid chromatography with electrochemical detection a specific and sensitive method for analysis. Peroxidatic metabolism of ANFT by prostaglandin H synthase (PHS) in the presence of N-acetylcysteine resulted in the formation of 2-amino-4-(5-nitro-2-furyl)-5-(N-acetylcystein-S-yl)thiazole (ANFT-MA). This thioether product has an oxidation potential significantly lower than ANFT. Rat urinary excretion of ANFT-MA was significantly decreased with peroxidase inhibitors, 6-n-propyl-2-thiouracil and methimazole. Inhibitors did not alter excretion of ANFT or prostaglandin E2, a PHS product of arachidonic acid metabolism. 1H and 13C-NMR were selected to explore potential structural differences between ANFT and FANFT which might explain preferential PHS metabolism of ANFT. Evidence for a "zwitterion" configuration for ANFT but not FANFT was observed. ANFT in the "zwitterion" configuration would be a better reducing co-substrate. Chemical synthesis and GC-MS fragmentation patterns identified 3-(2,3-dihydro-1-methyl-2-pyrrolyl)pyridine as a peroxidatic product of nicotine metabolism. This peroxidatic product was found in urine from a cigarette smoker in an amount approximately 6% that observed for continine. Thus, a potential rôle for peroxidative metabolism was demonstrated in man.
Mattammal
M B
MB
Geriatric Research, Education and Clinical Center, Veterans Administration Medical Center, St. Louis, MO 63125.
Lakshmi
V M
VM
Zenser
T V
TV
Davis
B B
BB
D000818:Animals; D002273:Carcinogens / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004563:Electrochemistry; D005200:FANFT / Q000031:analogs & derivatives* / Q000378:metabolism*; D011451:Prostaglandin-Endoperoxide Synthases / Q000494:pharmacology; D051381:Rats; D001749:Urinary Bladder Neoplasms / Q000139:chemically induced*
D002273:Carcinogens; C024885:ANFT; D005200:FANFT; D011451:Prostaglandin-Endoperoxide Synthases